Appetite: Journalfor Intake Research, 1983,4,195-234

Abstracts

Eighth International Conference on the Physiology of Food and Fluid Intake, Melbourne, Australia, August 23-26, 1983

An Official Satellite Symposium of the 29th Congress of the International Union of Physiological Sciences, Sydney, Australia, 1983

The following abstracts, in alphabetical order, were accepted for ICPFFI-8. Additional accepted abstracts were assigned to the day of meetings in common with the International Symposium on Olfaction and Taste: these are printed separately in the Common Day series.

Hypothalamic Obesity Despite Chronic Naloxone

SUE ANNE ASSIMON, RICHARD M. GOLD and JAMES M. BOCK University of Massachusetts, Amherst MA 01003, U.S.A.

In acute tests in rats the opiate blocker naloxone blocks the overeating of supermarket diet; blocks the overeating of rats with genetic obesity; and suppresses the diurnal and nocturnal feeding of chow diets by sated and deprived normal rats. Also in acute tests, naloxone suppresses feeding in rats with obesifying hypothalamic brain lesions. Chronic naloxone treatment prevents dietary obesity, but has a relatively transient effect on the intake of standard chow diet. We investigated the effects of chronic naloxone treatment via osmotic minipump upon the overeating and weight gain resulting from parasagittal hypothalamic knife cuts. Excessive weight gains seen following knife cuts were not prevented by either 0·16 or O' 32 mg/kg/h chronic systemic naloxone. Dosages were comparable to those that suppress dietary obesity. We suggest the hypothalamic obesity is not mediated via the activation of endogenous opiates.

Hypothalamic Modulation of Whole Body Metabolism

D. M. ATRENS, J. SINDEN, L. PENICAUD and J. LEMAGNEN Department of Psychology, University of Sydney, Sydney 2006, Australia and Col/ege de France, 75231 Paris, France

The effects of electrical stimulation of the hypothalamus on whole body metabolism were investigated using indirect calorimetry in rats. A single brief train of 50 Hz, 200 /lsec biphasic pulses produced an increase in respiratory quotient which peaked at 3-6 min and had returned to baseline by 12 min post-stimulation. In contrast, oxygen consumption showed a much slower onset and longer duration increase, peaking at 9-12 min and not returning to baseline until 27 min post-stimulation. Whereas there were some quantitative differences in the responses at lateral and ventromedial electrode sites, the general pattern was identical. These metabolic changes could be

0195-6663/83/030195+40 $03'00/0 © 1983 Academic Press Inc. (London) Limited

196 ABSTRACTS

dissociated from changes in activity and therefore support the position that the hypothalamus regulates energy balance by modulating energy expenditure as well as intake.

The Hedonic Perception of a Salty Taste

K. C. BERRIDGE, F. W. FLYNN, H. J. GRILL and J. SCHULKIN University of Pennsylvania, Philadelphia, PA 19104, U.S.A.

It has long been thought that hedonic changes in the perception of salt occur when the animal is in a state of sodium deficiency. This effect should be expressed in the facial responses of the animal when ingesting the salt. But it has never really been shown in any species. In the adult rat, we report that this phenomenon exists.

Oral infusions of hypertonic saline (0'5 M) provoke characteristic rejection and aversion consummatory facial responses in sodium replete rats. However, when subjected to natrorexigenic treatment (DOCA + furosemide) the same hypertonic saline infusions now provoke consumption, ingestive and positive consummatory responses without any of the aversive characteristics noted previously. Thus, the palatability of salt changes with the internal state of the animal.

Rapid Gastric Emptying: A Non-endocrine Autonomic Mechanism in VM H Obesity

D. A. BOOTH and J. P. DUGGAN Psychology Department, University of Birmingham, Birmingham B 15 2TT, U. K.

A striking prediction from simulation of the energy-supply theory was that obesity and hyperphagia following lesions of the ventromedial hypothalamus could be explained primarily by release of gastric emptying rate from its normal inhibition, presumed to be via ANS (Booth, 1976, 1978; Toates & Booth, 1974). Autonomic release of insulin hypersecretion in parallel was not necessary to predict the VMH syndrome, if the known hypertrophic response of the beta cell to persistent metabolic stimulation was allowed for. Insulin hypersecretion following VMH lesions can be attributed to beta cell stimulation or hypertrophy by faster absorption; indeed, the non-endocrine autonomic.hypothesis has been fully supported by subsequent calculations and data concerning ANS and metabolic controls of insulin secretion (Campfield, Smith, & Fung, 1982).

Ralph and Sawchenko (1978) reported slowed initial dumping of fluid loads in anaesthetised VMH rats but fluids are known to respond paradoxically to ANS abnormality (Davis & Booth, 1974). With maintenance chow we find that, early in the light phase when sham lesion rats empty at 0·41 ±0'09 g/h (N = 12), the stomachs of ambulatory VMH obese rats empty at 0·65 ±0'08 g/h (N = 8; p<O·OOI). This propor­tion of greater emptying speed was assumed in the computer modelling. There is also evidence of accelerated gastric digestion. In confirmation of Booth, Toates and Platt (1976), the satiating effect following absorption of starch was normal in VMH rats.

VMH obesity therefore arises from loss of the daytime slowing of gastric emptying, contrary to satiety-deficit and endocrine-autonomic hypotheses.

PHYSIOLOGY OF FOOD AND FLUID INTAKE

Dopaminergic Influence on Feeding and Drinking

ROBERT J. CAREY

VA Medical Center and SUNY Upstate Medical Center, Syracuse, NY 13210, U.S.A.

197

A series of experiments were conducted to evaluate the effect of lesion and pharmacological manipulations of brain dopamine on food and water intake in the rat. The initial experiments compared the effects of unilateral and bilateral destruction of forebrain dopamine neurons by intranigral injections of 6-hydroxydopamine on feeding behavior and body weight over a four-month post-operative interval. As compared with vehicle-injected controls, the unilateral and bilateral dopamine deficient rats showed persistent and equivalent reductions in body weight, attenuation of overnight water intake when food deprived and attenuation of the food intake suppression in response to d-amphetamine (1'0, 1·5 and 2·0 mg/kg). The dopamine lesions, however, did not alter the locomotor stimulatory effects of the same amphetamine treatment. The effects on spontaneous and pharmacologically-induced alterations in feeding and drinking behavior were correlated with the magnitude of hemispheric but not total brain level of dopamine. Subsequent studies showed that striatal and limbic dopamine deficits had differential contributions to the alterations of amphetamine-induced changes in locomotor and feeding behavior. These studies suggest that normative feeding and drinking behavior can occur with substantial bilateral deficits in dopamine but when dopamine is reduced below a critical level even unilateral deficits can produce marked and persistent deficits in feeding and drinking behavior.

Increased Dopamine and Serotonin in CSF during Severe Insulin­induced Hypoglycemia and Recovery in Freely Moving Rats

J. DANGUIR, J. L. ELGHOZI and D. LAUDE Neurobiologie des Regulations, College de France, 75005 Paris and Laboratoire Pharmaco ­logie, Faculte de Medecine Necker, 75015 Paris, France

The effect of insulin on dopamine (DA) and serotonin (5-HT) metabolites was determined in cerebro-spinal fluid (CSF) ofthe rat and compared with glucose levels in blood and CSF. CSF was continuously withdrawn from the third ventricle of freely moving rats at a constant rate of 1 j,d/min. Liquid chromatography with electrochem­ical detection was used for the direct assay of DA and 5-HT metabolites in CSF. The metabolites were stable for 1 h after insulin injection (6IU/kg i.p.). A progressive increase occurred thereafter in animals which had no access to food during the time of the experiment. The maximal effect was observed 2·5 h after insulin, with respective mean increases of 80% for dihydroxyphenylacetic acid, 4 7";~ for homovanillic acid and 33% for 5-hydroxyindolacetic acid. These increases were not observed when rats received glucose (1'5 g) 45 min after insulin or when food was available. The period for insulin-induced increase in DA and 5-HT metabolites corresponded to a maximum fall of glucose levels both in blood and CSF although the CSF glucose decrease was delayed when compared to the fall in blood glucose. These results are consistent with a possible role of brain glucose and/or brain insulin in the control of of central DA and 5-HT metabolism.

198 ABSTRACTS

Sensitivity of Different Nuclei of Rat Brain to the Anti-dipsogenic effect of Tachykinins

G. de CARO, M. MASSI, M. PERFUMI and F. VENTURI Institute of Pharmacology, University of Gamerino, 62032 Gamerino, Italy

Eledoisin (EL), physalaemin (PH) and substance P (SP) inhibit drinking elicited in the rat by i.c.v. angiotensin II (All), the i.c.v. anti-dipsogenic threshold doses being respectively 10, 50 and 100 ng per rat.

In this study we compared the anti-dipsogenic effect of tachykinins after injection into the lateral ventricles or into different brain nuclei in All-stimulated rats. The results are summarized in the Table where the effect of i.c. v. tachykinins is considered equal to 100. In parentheses, SP concentration (ng/mg protein) according to Dupont (Life Sciences, 1981, 28, 2317).

Brain nuclei

(Laterial venticle) HL, lat. hypoth. (2·1) HA, ant. hypoth. (4-8) POM, preopt. med. (7-8)

POL, preopt.lat. (3-9) SL, septi lat. 0·0) and Sm, septi med.

TABLE

EL PH

100 100 100 or less 100 or less

1000 to 2000 1000 to 2000 1000 to 2000 Over 10,000

Non detectable activity Non detectable activity

SP

100 100 or less

1000 to 2000 About 1000

Present data show that: brain nuclei have a selective sensitivity to tachykinins; in selected areas extremely low doses of EL (004 ng), PH (5 ng) or SP (10--100 ng) inhibit drinking; with the exception of POL, the largest is SP concentration in the nuclei, the largest is their sensitivity to tachykinins. In conclusion, POM and HA seem to be sites of a physiological anti-dipsogenic effect of the endogenous brain tachykinins SP and PH-like peptides.

A Contribution to a Correlation Between Drinking and Feeding Behaviour

L. DI BELLA, M. T. ROSSI and G. SCALERA Istituto di Fisiologia, Universita di Modena, 41100 Modena, Italy

Rats deprived of water, and offered a complete, equilibrated, ad libitum, dry, powdered diet, eat progressively less food, so that a negative material balance is produced, while the body weight decreases. The conclusion must be drawn that water deprivation induces an excitement of catabolism and a reduction of hunger, as if dopamine were injected into the cerebral ventricles. The finalistic exaltation of catabolism sets free the constitutive water of tissues, which prevails over the combustion water deriving from the tissue organic burnable substances, and is found to be fully sufficient for at least five days of water deprivation. Combustion water is a poorer and a slower means to satisfy the pressing water needs of dehydrated rats. The

PHYSIOLOGY OF FOOD AND FLUID INTAKE 199

most profitable substances for burning are the lipids which can liberate over 100% of combustion water. These experimental results are in harmony with the behaviour of some healthy human beings, where overdrinking, overfeeding and fatness often go hand in hand.

Brain Angiotensin Converting Enzyme and Thirst

R. DINICOLANTONIO, F. A. O. MENDELSOHN and J. S. HUTCHINSON Department of Medicine, University of Melbourne, Austin Hospital, Victoria 3084, Australia

The finding of a brain renin-angiotensin system raises the possibility that angiotensin II generated within the central nervous system is involved in the elicitation of thirst (Chen et al., Experimental Brain Research, Suppl. 4,157-168,1982). To test this hypothesis we have examined, in the rat, the effect of intracerebroventricular (i.c.v.) administration of the angiotensin converting enzyme (ACE) inhibitor, captopril, on dnnking due to various manoeuvres. I.c.v. captopril (7 pg) significantly (t = 11·2, p <0·01) attenuated the dipsogenic response to i.c.v. angiotensin I (200ng) for up to 2 h. The same dose of captopril significantly (t = 2· 3, p < 0'03) potentiated the dipsogenic response to i.c. v. angiotensin II (100 ng) but failed to alter the dipsogenic response to i.c. v. carbachol (200 pmol). Pretreatment with i.c. v. captopril (7 j1g), for 30 in, failed to markedly alter the cumulative water intake of 24 h water deprived rats. However a small, significant (t = 1'8, p < 0'05), 8% decrease in water intake was noted 60 min following the return of water. Pretreatment with ic.v. captopril (7 j1g), for 30 min failed to alter the cumulative water intake of rats treated intra peritoneally with hypertonic saline (0'75 M in 1% of the body wt); a dipsogen believed to act independently of angiotensin-mechanisms. From these studies it would appear that central ACE plays only a minor role in water-deprivation-induced thirst.

Reduced Insulin Content in the Brains of Genetically Obese (Zucker) Rats

D. DORSA, D. BASKIN, H.IKEDA, L. STEIN, D. FIGLEWICZ, D. PORTE, JR. and S. WOODS VA Medical Center and University of Washington, Seattle, WA 98108, U.S.A.

Circulating insulin levels may serve as an indicator of body weight which is monitored by the central nervous system. We hypothesized that diminished access or reception of this endocrine signal in the brain might be responsible for the hyperphagia which occurs in fatty (fa-fa) Zucker rats. To test this hypothesis, we have measured brain insulin content in homozygous "normal" (Fa/Fa), heterozygous "lean" (Fa/fa) and homozygous "fatty" (fa/fa) Zucker rats. An acid extraction of various brain regions was performed, and insulin was measured using a highly sensitive (0·02 j1U /tube) RIA. Regional brain insulin in the table contents in j1 U /g wet wt. of tissue are shown

Insulin content in Fa/Fa brains is similar in magnitude and distribution to other non-obese rats. Insulin content is significantly reduced in Fa/fa brain, but plasma insulin levels are comparable in these two groups. In contrast, fa/fa rats showed even

200

O. Bulb. ------- -

Fa/Fa Lean Fa/fa Lean fa/fa Fatty

10·3 ± 1·0 < 1-4±0·4 <2·1 ±0·4

ABSTRACTS

TABLE

Hypothal. Hippoc.

S·6±0·6 4·S±0·6 <0·9±0·2 3·S±0·9 < 1·8±0·6 2·S±0·S

H. Brain Cortex

4-4±0·3 4·9±0-4 2-4 ± 0-4 2·S±0·S 2·2±0·3 2·1±0·S

more dramatic reduction in regional brain insulin content associated with plasma insulin levels five to six times higher than the other groups. The results suggest that insulin uptake or binding in the brain of Zucker rats is deficient, and supports the hypothesis that Zucker rats overeat because they fail to recognize body weight signals mediated by insulin.

Responses to Methionine Deficiency and Imbalance in Sheep

A. R. EGAN and B. C. RADCLI FFE Department of Animal Sciences, Waite Agricultural Research Institute, Glen Osmond, 5064 Australia and School Agricultural Forestry, University of Melbourne, Parkville, 3052 Australia

Ruminant lambs fed ground wheaten straw pelletted with minerals and urea (WS), received per abomasum an infusion of a complete mixture of amino acids (A A) (Egan & Rogers, Australian Journal of Agricultural Research, 29, 1263-1279, 1978). This provided adequate methionine (MET) and threonine (THR) for slow growth, and a slight excess of other essential amino acids. In a series of experiments removal of MET or MET + THR caused a reduction in WS intake over ten to 20 days. During this period, offering alternative low protein diets including WS with aniseed flavouring (WS-A) resulted in increased sampling activity and first meal intake, but a subsequent decrease in, interest in and intake of alternative diets. Simultaneous presentation of the WS-A diet and infusion of mixture AA resulted in sustained higher intake from the first meal taken; but if the feed offered was not changed, intake recovery was delayed. In sheep fed the WS diet and infused with AA per abomasum, methionine imbalance was induced by infusion of a large excess of a mixture of all amino acids excluding methionine (3AA-M). Intake fell to zero in the second day, and could not be repaired over four days by infusion of water or of a complete mix (3AA). Presentation of the WS­A diet stimulated feed sampling activity by most sheep in this period, but intake was recovered only if water or the 3AA mix, was infused. Changes in plasma amino acid concentrations were correlated with the pattern of responses. A simple physiological model is proposed.

Cardiovascular Changes Caused by Drinking in the Rat

MARK D. EVERED, JAVED SIDDIQI and ALICE J. JACKES Department of Physiology, University of Western Ontario, London, Canada N6A 5C1

It has been observed in many species including man that drinking water or other fluids increases arterial pressure and/or heart rate. We have studied the cause of drinking-related pressor responses in water-deprived rats with chronic arterial

PHYSIOLOGY OF FOOD AND FLUID INTAKE 201

cannulae. Arterial pressure rose 10- 25 mmHg within a few seconds after drinking started and returned to normal only when drinking ceased (voluntarily or water removed). Heart rate increased or did not change; it rarely fell. The pressor response was abolished by the a-adrenergic antagonist phentolamine (10 mg/kg, s.c.) suggesting that it is mediated by the sympathetic nervous system. However, it is not caused by general arousal, postural changes or the motor act of licking because blood pressure did not change in thirsty rats vigorously licking cold but sealed spouts or cool jets of air. Blood pressure increased when water was infused directly into the mouth (oral cannula) at rates normally drunk (1·6 ml/min) but only if the water was swallowed. Pressure fell when swallowing stopped even though the infusion continued and water dribbled from the mouth. Infusions at the same rate into the lower esophagus or stomach did not increase arterial pressure. Infusions into the naso- or oropharyngeal region at 1/ 10 this rate stimulated large pressor responses but also bradycardia, characteristic of the "dive" reflex protecting airway patency. It appears that the drinking-related cardio­vascular changes in the rat are part of the series of somatic and autonomic events coordinated during the deglutition phase of ingestion.

Supported by the MRC of Canada.

Salt Appetite in Hamsters

DOUGLAS A. FITTS, and JOHN B. SIMPSON Department of Psychology, University of Washington, Seattle, WA 98195, U. S.A.

Earlier research has often suggested that hamsters fail to show a sodium appetite under conditions, such as mineralocorticoid treatments or colloid dialysis, which provoke a robust sodium ingestion in other rodents, such as the rat. We have found, in contrast, that it is indeed possible to show sodium appetite in the hamster. In a two­bottle choice situation between water and 0·15 M NaCI, untreated hamsters consumed virtually all fluid as water, with no voluntary sodium intake occurring. A single s.c. injection of polyethylene glycol led to increased intake of 0·15 M NaCI but not of water in this two-bottle choice situation. Positive water and sodium balances were measured over the 48 h following the single injection, which reduced measured intravascular volume by 30%. We have also found that daily injections of DOC A increased intake of 0·15 M NaCI by the third day of injection. The mineralocorticoid treatment also produced increased body weight, hypernatremia, expanded intravascular volume, and reduced fecal sodium content. Adrenalectomy of hamsters produced progressive negative sodium balance, reduced plasma volume, and decreased food intake, all of which were reversed with subsequent DOCA treatments. We include, in contrast to earlier studies, that: (i) miner~locorticoids, then, appear to be an effective control over sodium homeostasis in this species; and (ii) hamsters will indeed show a salt appetite under appropriate experimental conditions.

Glucose Responsive Neurons in the Rat Hypothalamus: An in vitro Slice Study

M. FUKUDA, T. ONO, H. NISHINO and K. SASAKI Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Toyama, 930-01, Japan

Rat hypothalamic glucose responsive neurons, which are related to glucose regulation and feeding control, are well accepted. By recording extracellular action

202 ABSTRACTS

potential in ill vitro rat hypothalamus slices containing ventromedial (VMH) and dorsomedial (DMH) nuclei, and lateral area (LHA) of the hypothalamus, hetero­geneous glucose effects in all of these regions were studied. Spontaneous activity of 256 VMH, 103 DMH and 59 LHA neurons was observed in coronally-oriented rat hypothalamic slices, perfused in low glucose concentration (5'5 mM). Increasing glucose concentration (20 mM) produced three response patterns in all regions: excitation, excitation followed by inhibition and inhibition. In the VMH, most were excitation; in the LHA, most were inhibition; in the DMH, excitation and inhibition responses were about equal. When the D MH or VM H were isolated from the other nuclei, the changes in ratios of the response patterns were insignificant. From these in vitro results it is suggested that the heterogeneous glucose responses of neurons in the VMH, DMH and LHA depend on the chemoresponsiveness of the neurons and not necessarily on influence from neurons in other regions.

Sodium Homeostasis in the Decerebrated Rat

H. J. GRILL and J. SCHULKIN University of Pennsylvania, Philadelphia, PA 19104, U. S.A.

Little is known about the role of the lower brains tern in sodium homeostasis. In this investigation decerebrated and control rats were implanted with an oral fistula which was used to deliver saline into the mouth. We found that decerebrates did not increase their saline intake over baseline following natrorexigenic treatment (DOCA + furosemide) while intact rats did increase. These behavioral results and those of others (e.g., see Wolf & Schulkin in Biological and Behavioral Aspects of Salt Intake, 1980 or Denton, The Hunger for Salt, 1982), point to the essential role of the upper brainstem and forebrain in mediating the regulatory phase of salt appetite.

We also monitored the sodium excretion of rats that were given a sodium load or maintained on a sodium-deficient diet. These results suggest that physiological compensatory mechanisms are intact in the decerebrated rat. Although more slowly than the control rats, the decerebrates did excrete the excess sodium; they also retained sodium while being fed a sodium-deficient diet.

These results are discussed in the context of the evolution of brain mechanisms for ingestive behavior.

Investigations into How Pentagastrin Depresses Food Intake by Sheep

W. L. GROVUM Department of Biomedical Sciences, University of Guelph, Canada N1 G 2W1

The anorexic properties of pentagastrin (PG) were investigated by comparing the effects of systemic infusions (via jugular vein) with those of (a) central infusions (carotid artery), (b) hepatic infusions (portal vein), (c) gastric infusions (coelic artery) and (d) intestinal infusions (mesenteric artery) on food intake by hungry sheep. Another group of halothane-anaesthetized sheep were used to study the influence of pentagastrin on the activity of tension receptors in the reticulum, this being recorded from single vagal

PHYSIOLOGY OF FOOD AND FLUID INTAKE 203

fibres isolated under liquid paraffin in the mid-cervical region of the neck. Systemic infusions of between 0·8 and 18 J.lg PG/kg/h inhibited intake in a dose-related manner. The brain might have mediated part of the anorexia at low dose rates because, for example, five hungry sheep ate 202" and 174bc g food /20 min during systemic and central infusions of 1 J.lg PG/kg/h whereas the control was 195'c g/20 min and 155b and 167b g/20 min were eaten respectively at 9 J.lg/kg/h (p < 0'05). The liver metabolized the PG but did not mediate the anorexia because infusions of 3 and 9 J.lg PG/kg/h into five sheep resulted in higher intakes (p<O'OI) for hepatic (214 and 228g/3h) than for systemic infusions (160 and 97 g/3 h respectively, the control intake being 241 g/3 h). Similar results were obtained for infusions of PG into the coeliac and mesenteric arteries. This was not expected since the activity of reticular tension receptors was increased by coeliac injections of pentagastrin as well as by reticular distension which previously haB been shown to reduce intake.

Water Balance and the Area Postrema/cm Nucleus of the Solitary Tract

THOMAS M. HYDE and RICHARD R. MISELIS Laboratories of Anatomy, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A.

Abdominal vagal sensory afferents distribute in part over the area postrema (AP) and the adjacent caudal medial nucleus of the solitary tract (cmNTS). Lesions of the AP /cmNTS can be made without direct damage to the underlying vagal motor complex. In such a preparation, profound changes in fluid intake, urine output and salt appetite occur. Lesioned rats develop an immediate post-operative polyuria which persists for many months. Lesioned rats also develop a relative polydipsia and display elevated water/food ratios. Increased urinary sodium losses accompany the increased volume. This sodium loss may account for the increased 3% NaCI solution intake in these rats. Furthermore, lesioned rats lag in concentrating their urine during 24 h of total deprivation. However, by the end of the deprivation period, lesioned rats concentrate their urine as well as controls. This defect in urine concentration correlates with the lag in volume conservation seen in a 24h test under total deprivation conditions. The increased urine volume and sodium loss, coupled with the impaired concentrating ability, suggest an alteration in the physiological controls over fluid balance. The increased water intake and water/food ratios may be adaptive behavioral compensations for this aberrant physiology.

Supported by GM 27739 and 07170.

lesions of the lateral Portion of the lateral Parabrachial Nucleus: An Exaggerated Drinking Response to All in the Rat

A. K. JOHNSON and L. E. OHMAN Department of Psychology and the Cardiovascular Center, University of Iowa, Iowa City, IA 52242, U.S.A.

Changes in blood pressure and volume are known to activate mechanisms controlling body fluid balance. Recent anatomical evidence suggests that cardio­vascular information may travel from the medulla to the hypothalamus via the

204 ABSTRACTS

para brachial nucleus (PBN). The nucleus tractus solitarius (NTS), an area that receives inputs from neurons carrying cardiovascular information, sends a major projection to the lateral PBN (LPBN). The LPBN projects to the hypothalamus, particularly the median preoptic nucleus, a prominent component of the anteroventral third ventricle region (AV3V). To test the hypothesis that the LPBN is involved in the control of fluid balance, rats with bilateral lesions of the lateral portion of the lateral LPBN (LLPBN) and control animals were tested for drinking in response to subcutaneous adminis­tration of All (\'5 mg/kg), isoproterenol (100 pg/kg, 30 pg/kg), hypertonic saline (12~-;; , 4/~), and saline vehicle. LLPBN lesioned animals drank significantly more than controls to both doses of All (p < 0'05). These results suggest that the LLPBN is a component of an inhibitory thirst pathway, which attenuates drinking to high circulating All levels.

Hypothalamic Facilitation of Biting

JOEL M. KAPLAN and SAMUEL M. FELDMAN Department of Psychology, New York University, New York, NY 10003, U.S.A.

We have confirmed Smith's finding (Physiological Behavior, 8, 617-621, 1972) that electrical stimulation of the lateral hypothalamus (ESLH) that elicits oral behavior (e.g. feeding, drinking, gnawing) also facilitates the biting response to a tactile probe applied to the perioral region. Rats that showed little or no biting of a probe stick in the absence of ESLH were tested in a cloth harness to which they had been previously adapted. Both extent of the tactile receptive field for eliciting the perioral response (POR) and probability of its elicitation by tactile stimulation at discrete points within the receptive field increased with ESLH intensity. In stimulus-bound feeders, we also examined the degree to which the ESLH-facilitated biting was coupled to feeding behavior. Sensitivity of the POR was measured (1) before rats had any exposure to food during ESLH (i.e. before feeding responses had a chance to "emerge") and (2) after experienced ESLH eaters declined to eat, having just consumed as much as 50 g of wet mash (3: 2, water: lab chow) during a single ESLH test session. Our results showed that perioral responding was relatively unaffected by experience with food or by bloating. We conclude that facilitation of the POR is an unconditioned feature ofESLH in stimulus­bound eaters (and gnawers, etc.) and that its sensitivity is solely a function of the physical parameters of electrical and tactile stimulation.

Role of Right Atrial Receptors in Control of Drinking

SUSAN KAUFMAN University of Alberta, Edmonton, Canada T6G 2G3

When the superior vena caval/right atrial junction was stretched with an inflatable balloon, water intake was significantly attenuated in conscious, unrestrained rats subjected to 24 h water deprivation or s.c. injection of isoprenaline. Inflation virtually abolished the drinking to i.p. injection of hyperon co tic colloid (hypovolaemia) but had no affect on drinking to i.v. hypertonic saline or intracerebro-ventricular angiotensin II. These effects were not secondary to changes in arterial or central venous pressure.

PHYSIOLOGY OF FOOD AND FLUID INTAKE 205

Moeover, stretching the vein/atrial junction resulted in a reflex natriuresis and diuresis that was mediated by neither ADH nor nervous input to the kidney, suggesting that an, as yet uncharacterized, factor may playa role in both the renal and behavioral responses. Indeed, I have recently shown that atrial extract, in addition to its potent natriuretic and diuretic activity, does also attenuate the drinking response of hypovolaemic, but not hyperosmolar, animals. These results lend credence to the hypothesis that volume receptors on the right side of the heart are involved in controlling water intake possibly through both neural and hormonal pathways.

Effect of Lesions of the Area Postrema and Caudal-Medial Portion of the Nucleus of the Solitary Tract (AP/cmNTS) on Macronutrient Selection by Rats

NANCY J. KENNEY, JON N. KNOTT and CHRISTINE GANFIELD University of Washington, Seattle, WA 98195, U.S.A.

AP /cmNTS lesions result in a sustained suppression of body weight and transient decrease of food intake of rats. This study examines the effect of such lesions on intake of fat, protein and carbohydrate by rats in a "self-selection" situation. Lesioning occurred after a three week, diet-adaptation period. Daily intakes of each commodity oflesioned and sham-operated rats were measured for one five-day period prior to and four consecutive five-day periods subsequent to lesioning. During the first two post­surgery periods, the rate of weight gain and total daily caloric intakes of lesioned rats were suppressed compared with those of controls. The reduction oftotal caloric intake was due entirely to a decreased intake of fat. Fat intake averaged 42·0± 15·6 kcal prior to lesioning compared to 1O·2±4·3 and 18·2±8·0kcal during the first two post­ablation test segments, respectively. Intakes of protein and carbohydrate of lesioned rats and of all three commodities of sham-lesioned animals did not change from baseline levels. Daily caloric intakes and intakes of fat of lesioned rats returned to presurgery levels during the final ten days of the study. Thus, in the "self-selection" situation, the reduction offood intake which immediately follows AP /cmNTS lesions is due to a specific decrease of the number of calories taken as fat and does not reflect a general suppression of ingestion of all dietary components.

Supported by research grant AM22024 to NJK.

Histaminergic Mediation of Drinking Elicited by Pregastric Stimulation with Food

F. SCOTT KRAL Y Department of Psychology, Colgate University, Hamilton, NY 13346, U.S.A.

Food-contingent stimulation of the oropharynx (pregastric) is reported to elicit drinking and release gastric mucosal histamine and pancreatic insulin in the rat. The mediation of such food-related drinkng by histamine and insulin, each dip so genic when injected subcutaneously (s.c.), was examined. Drinking elicited by s.c. histamine diphosphate (1·24-20mg/kg) was abolished by combined antagonism of Hi and H2 histamine receptors with intraperitoneal (i.p.) 1 mg/kg dexbrompheniramine plus 16 mg/kg cimetidine. Such histaminergic antagonism does not inhibit drinking non-

206 ABSTRACTS

specifically, because it failed to inhibit drinking after 8-h or 24-h water deprivation or after s.c. serotonin (0·63 mgjkg 5-HT creatinine sulfate complex). Drinking elicited by s.c. bovine pancreatic insulin (5 U jkg) was abolished by the same combined antagonism of Hl and Hz receptors. Finally, drinking elicited by pregastric food-contingent stimulation (in rats sham feeding with open gastric fistula) was abolished by combined antagonism of Hl and Hz receptors. In summary, these results (1) show that the dipsogenic effects of exogeneous insulin and histamine are mediated by histamine receptors, consistent with the report that exogeneous insulin releases gastric mucosal histamine, and (2) suggest that endogenous insulin and histamine playa major role for drinking elicited by pregastric stimulation with food in the rat.

The Satiety Effect of Several Metabolites Might Depend on the Rapid Generation of Reducing Equivalents

w. LANGHANS, U. DAMASKE and E. SCHARRER

/nstitut Physi%/ gische Chemie und Ernahrungsphysi%gie, Universitat Munchen, 0-8000 Munchen, F.R.G.

Although it is doubtful whether glycerol normally contributes to food intake regulation, the still unknown mechanism whereby exogeneous glycerol loads reduce feeding might have physiological significance. For further investigation of this mechanism we subcutaneously injected male rats with isoosmotic solutions of glycerol (G) or dihydroxyacetone (DHA) and measured food intake at various times up to 24 h after injections. Both compounds are phosphorylated to glycerol-3-phosphate (G3P) and dihydroxyacetonephosphate (DHAP), but G3P is then rapidly oxidized to DHAP thus providing reducing equivalents (RE). Injection of G significantly inhibited feeding compared to saline-injected controls whereas injection of DHA did not. In addition, further similarly designed experiments revealed that malate (MAL) and D,L-3-hydroxybutyrate (3HB) also reduced food intake, but not oxaloacetate (OXAC) and acetoacetate (ACAC). Rapid oxidation of MAL and 3HB to OXAC and ACAC by primarily hepatic membrane-bound enzymes also provides RE. Thus, a common mechanism related to the rapid generation of RE by the first oxidative step in the metabolism of G, MAL and 3HB might contribute to the hypophagia following subcutaneous injection of these compounds.

In Rats, the Effects of 3-h Deprivation on Blood Glucose level and Subsequent Intake are Correlated Throughout the Day

C. LARUE-ACHAGIOTIS and J. LEMAGNEN

Col/ege de France, 75231 Paris, France

Evidence has been provided that meal size in free-fed rats is not determined by and not proportional to the energy deficit at the start of the meal; rather it anticipates further expenditures. By contrast when a premeal energy deficit is produced by a short withdrawal offood, meal size increases proportionally as a function ofthe induced fall in blood glucose level. In the present work, free-fed rats were submitted to 3 h of food deprivation starting at 0,3 or 6 h after the beginning of the dark or the light periods. The fall in blood glucose level induced by these six deprivation periods was measured in a

PHYSIOLOGY OF FOOD AND FLUID INTAKE 207

first group. In another group the size of the first meal and the 3-h subsequent intake were measured. It was shown that the deprivation-induced hypoglycemia decreased from the beginning to the end of the night. Likewise the effect of deprivation on the subsequent first meal and 3-h intake decreased. During the daytime, only the latest 3-h deprivation period affected the blood glucose level and the 3-h intake. It is suggested that the deprivation-induced increase in meal size is related to and plausibly determined by deprivation-induced hypoglycemia.

Infusions of Intracerebroventricular Insulin Decreases Plasma Catecholamines of Free-feeding Rats

E. C. LOTTER and R. G. CAMPBELL Department of Psychology, Nazareth College and Department of Medicine, University of Rochester, Rochester, NY 14610, u.s.A.

We have reported that insulin infused into the lateral cerebral ventricle of baboons decreases food intake and body weight with no reliable effect on basal plasma immunoreactive insulin (lRI). Moreover, injections of norepinephrine (NE) into the hypothalamus elicit an immediate rise in plasma IRI. The NE-stimulated insulin response is similar to rats eating a carbohydrate meal. The present study investigates the relationship between the peptide hormone insulin and plasma catecholamines. Rats deprived of food for 5 h were infused with insulin into the lateral cerebral ventricle of free-moving unanesthetized Wistar rats for I h/day. Cerebro-spinal fluid (CSF) contained either artificial rat CSF or CSF plus rat insulin (lOOmU/IS),). Infusion of CSF alone for two weeks had no reliable effect on either epineprhine, norepinephrine or glucose levels. Addition to the infusate of the insulin for the same period of time resulted in a significant decrease of plasma epinephrine and norepinephrine (p < 0·05). No change in plasma glucose levels were observed. During a meal, plasma NE levels were significantly lower in the insulin-treated group (p < 0·05). These data suggest that the decrease in plasma catecholamines without any change in glucose levels may account for the observed decrease of food intake associated with insulin infusions.

Renin-dependent Water Intake

JOHANNES F. E. MANN, DETLEV GANTEN and ALAN KIM JOHNSON Departments of Medicine and Pharmacology, University of Heidelberg, FR.G., and Department of PsychologV University of Iowa, Iowa City, IA 52242, U.S.A.

Thirst following intraperitoneal (i.p.) injections of renin has only been observed when plasma renin activity (PRA) rose to supraphysiological levels (Stricker et ai., Science, 1976, 194, 1169). However, the active component of the renin~angiotensin ~ystem (RAS), namely angiotensin II (AlII), was not measured. We re-investigated the formation of AI [ after i.p. renin injections in conscious rats. Various doses of renin (0·1 ~ 60U/kg) were injected and rats killed after 15,30 and 60 min for the determination of PRA, PR-concentration, and plasma All levels. Dose-dependent increases of PRA, PRC, and All levels were observed. Linear correlations between the three parameters could be calculated. Specifically, All generation did not level off with high renin doses. However, PRA's under the conditions studied were considerably lower (maximally

208 ABSTRACTS

200 pmol/hr/ml) than previously reported. In addition, All levels generated by exogenous renin were well within the range of the endogenous RAS, e.g., following [3-adrenergic stimulation (Johnson et al., American Journal of Physiology, 240: R229, 1981, and Mann et al., American Journal of Physiology, 238: R372, 1980). We conclude that even exceedingly high doses of exogenous renin (given i.p.) generate All levels within the range of the endogenous RAS.

Water and Na Intake in Rats After Various Diuretic Treatments

M. J. MCKINLEY, D. A. DENTON, J. F. NELSON and R. S. WEISINGER Howard Florey Institute of Experimental Physiology and Medicine, University of Mel­bourne, Parkville, Victoria 3052, Australia

Despite widespread clinical use of diuretics, there has been little study of water and Na intake following diuretic-induced fluid and electrolyte loss. We have studied water intake in 12 rats following urine loss induced by furosemide (20 mg/kg) (F); chi oro thiazide (10mg/kg) (C); acetazolamide (lOOmg/kg) (A); MK 447 (1 mg/kg) (M); or normal saline (S). Water drinking in response to hypovolaemia was small (5-15% of water loss) and slow in onset in the first 6 h. After 6 h, rats treated with F drank 6·9± 1·3 ml/kg (mean±SEM) after losing 46± 1 ml/kg urine, and those treated with A drank 3·3 ± 1·1 ml/kg and lost 34 ± 2 ml/kg urine. Water intake after CorM was not significantly different from S (0·6 ± 0·4 ml/kg). Even after 24 h, rats had not restored body weight loss after treatment with any of these diuretics. In another experiment, rats were allowed access to both water and 0·5 M NaCl solution after treatment with F, A, M or S. A pronounced increase in NaCI intake occurred in the 24 h following treatment. NaCI intake occurred earliest with A (usually within 4 h) whereas it commenced 7-12 h after treatment with F or M. By 24 h body weight was restored. These data indicate that diuretic-induced hypovolaemia is a weak stimulus to thirst in rats and that there are differences in patterns of NaCl and water intake depending on the diuretic administered.

Regulation of Angiotensin II Receptors in the Subfornical Organ during Dehydration

F. A. O. MENDELSOHN, J. M. SAAVEDRA, G. AGUILERA and K. J. CATT Endocrinology and Reproduction Research Branch NICHD and Laboratory of Clinical Science, NIMH, NIH, Bethesda, u.s.A.

The marked elevation in plasma angiotensin II (All) during dehydration, and the ability of All to stimulate drinking by a direct action on the subfornical organ (SFO), suggest that All is involved in the control of thirst and water intake. Since blood-borne All binds to circum ventricular structures and is concentrated in the SFO, we analyzed All binding sites and their regulation in discrete brain regions during dehydration. We previously observed reciprocal changes in adrenal and smooth muscle All receptors during sodium deficiency. In the brain, All receptors were measured by 125I_AII binding in the presence of protease inhibitors in membranes of specific regions microdissected on ice from brains of controls and water-deprived male rats. These receptors were of high affinity (Ka = 4·4 x 109 M - 1) and low capacity (9·1 fmol/mg

PHYSIOLOGY OF FOOD AND FLUID INTAKE 209

protein), with selectivity for All analogs similar to that of adrenal receptors, i.e. [Sarl]AII was 10 times, desAspl-AII was equipotent, and AI was 0·001 times as potent as All in displacing 125I_AII. The SFO content of All receptors was 0·26±0·05 fmol (S E, N = 10) and rose significantly to O· 38 ± 0·06 fmol/SFO in rats deprived of water for 48 h (p > 0·05). In contrast, All binding was unchanged in OVL T, area postrema and cerebral cortex. These results demonstrate that specific All receptors in the SFO increase by about 50% during dehydration. This could provide a mechanism by which enhancement of All-mediated drinking responses during dehydration accelerates the correction of volume depletion.

Energy Balance under the Control of the Area Postrema and Abdominal Visceral Afferents of the Vagus

RICHARD R. MISELlS, THOMAS HYDE, ROBERT SHAPIRO and RICARDO ENG University of Pennsylvania, Philadelphia, PA 19104, u.s.A.

Lesions of the area postrema (AP) and caudal medial nucleus of the solitary tract (cmNTS) cause transient hypophagia and body weight loss followed by recovery of feeding and establishment of a new reduced body weight growth curve. They defend the new body weight; have a heightened response to palatable foods but maintain the same accelerated growth curve as shams on this diet; show a deficit in the feeding response to glucoprivation but recover and have a longer latency response. Similar to peripheral subdiaphragmatic vagotomy, the AP/cm NTS lesion reversed hyperphagia and obesity of hypothalamic origin. This reversal phenomenon has been attributed to loss of motor components of the vagus. Since the AP/cmNTS lesion does not directly damage the motor nucleus of the vagus but does lesion the terminal field of abdominal visceral afferents, it is likely that the sensory components of the vagus are extremely important in the regulation of body weight and control of food intake. Neuroanatomical studies using HRP and cholera toxin conjugates ofHRP show afferents ofthe subdiaphragma­tic vagus lying mainly in the AP/cmNTS; gastric afferents mainly in the gelatinosajust anterior to the AP; afferents of the portal vein below the AP; and the motor neurons of the vagus with dendrites entending up into the overlying cmNTS.

Selective Enhancement and Suppression of Sodium Appetite by Low or High Doses of Systemic Captopril

K. MOE and A. N. EPSTEIN Department of Biology, University of Pennsylvania, Philadelphia, PA 19174, u.s.A.

To examine the role of angiotensin II (A II) in sodium appetite, the formation of endogenous A II was blocked in rats by the peripheral administration of captopril (Squibb), a converting enzyme inhibitor which blocks the conversion of A I to the active peptide, A II.

Doses of i.v. captopril which blocked conversion both peripherally and centrally suppressed sodium appetite elicited by sodium depletion but had no effect on the sodium preference of sodium-replete rats. The lack of effect on sodium preference

210 ABSTRACTS

suggests that the captopril effect on sodium appetite is a selective one and not due to general suppression of behavior. Moreover, these results suggest that the rise in All levels known to occur during sodium depletion is important to the arousal of sodium appetite.

Lower doses of captopril which blocked conversion only in the periphery, as indicated by an intact dipsogenic response to central injection of A I, significantly enhanced the sodium appetite associated with depletion but had no effect on DOCA­induced sodium appetite or on sodium preference. Thus, A If probably plays little or no role in the latter two forms of salt ingestion. The enhancement of the appetite elicited by sodium depletion is most likely the result of a "spill-over" of excess A I into the brain. In addition, this enhancement suggests that elevated A II levels act within the brain to produce sodium appetite.

Neural Circuits Associated with Exploratory Locomotion and with the Procurement Phase of Ingestive Behaviours

G. J. MOGENSON, Department of Physiology, The University of Western Ontario, London, Canada

The nucleus accumbens, and its mesolimbic dopamine afferents from the ventral tegmental area, and GABAergic efferents to the subpaJlidal region, have been implicated in water intake (Jones & Mogensen, Canadian Journal of Physiology and Pharmacology, 1982, 60, 720-726, Mogensen & Sztorc, Behavioral Neural Biology, 1982,34,384-393. These neural circuits appear to contribute to exploratory and goal­directed locomotion, which are fundamental to the procurement phase of water and food intake. According to recent anatomical and electrophysiological studies the hippocampus may be the course of afferent signals of the accumbens and the mesencephalic locomotor region may be the target of efferent signals from the subpallidal region (Swanson, Mogenson, & Wu, Society for Neuroscience, 1982, Abstract No. 48.23). The possibility that these neural projections also contribute to exploratory locomotion is supported by the results of neuropharmacological­behavioural experiments, which will be presented.

Effects of Atrial Extract on Fluid and Electrolyte Balance in Conscious Rats

M. MOORE-GILLON and S. KAUFMAN University of Alberta, Edmonton, Alberta T6G 2G3, Canada

Atrial myocardium contains a powerful natriuretic and diuretic factoL We have examined the effects of crude atrial extract on fluid and electrolyte balance in the conscious rat. Male inbred rats were prepared with inferior vena caval cannulae, aortic cannulae, truncated bladders and intraperitoneal sacs made from semi-permeable membrane. One week later, a 25% w jw solution of polyethylene glycol (20 M) in isotonic saline was injected into the sacs (15 mljkg body wt). At 7·75 h post-injection, the sacs were drained and at 8 h water returned. Two minutes prior to and 13 min after water was offered, the rats were injected i.v. with either isotonic saline (S), ventricular extract (VE) or atrial extract (AE). AE and VE were obtained from male rats of the same inbred

PHYSIOLOGY OF FOOD AND FLUID INTAKE 211

strain. Rats drank significantly less after AE injection than after either VE or S. (AE =0·80±0·31 ml/100kg b.wt, VE= 1·71 ±0·21 ml/ lOOg b.wt, S= 1·77±0·12ml/ 100g b.wt, n = 13, p < 0·01.) Urine volume and Na output were also significantly greater in the AE rats. In contrast to these results, AE had no effect on the drinking response to i.v. 2 M

NaCl (0·5 ml/100 g b.wt). Blood pressure and heart rate of the conscious, unrestrained rats fell when AE was administered (LlBP= -17 mmHg, LlHR = -44 bpm). These results indicate that a factor present in crude extract of rat atria reduces drinking in response to hypovolaemia as well as promoting increased urinary loss of sodium and water and that these effects are not secondary to an increase in arterial blood pressure.

Reduction in Food Intake Following Systemic Administration of Amphetamine is Reversed by Injecting a Dopamine Antagonist into the Nucleus Accumbens

E. MUNN and G. J. MOGENSON Department of Physiology, University of Western Ontario, London, Canada, N6A 5C1

Food intake is markedly reduced by amphetamine, one of the classical anorectic drugs. Since amphetamine releases dopamine from axon terminals and blocks its reuptake, one possibility is that the anorexIa is dopamine-mediated. In support of this suggestion, it has been reported that the amphetamine anorexia is reversed by the systemic administration of dopamine antagonists (Burridge & Blundell, Neuro­pharmacology, 1979, 18, 453-457). The present study was undertaken to see whether administering a dopamine antagonist centrally into the nucleus accumbens, a region that receives dopamine projections, would also reverse amphetamine anorexia. In rats with chronic bilateral cannulae in the accumbens, measures offood intake were made after 21 h of food deprivation. The administration of amphetamine (2mgjkg, i.p.) reduced food intake during a 30min observation period by approximately 75- 80% (from 12-16 g to 1·5-4·5 g). When haloperidol (0·62 Ilg and 1·25 Ilg in 0·5 111) was injected bilaterally into the accumbens, food intake following administration of amphetamine was reduced by approximately 30-35% and 20-25% respectively (p<0·05). These observations implicate the mesolimbic dopamine projection to the nucleus accumbens in amphetamine anorexia.

Supported by NSERC of Canada to EM.

Some Perspectives on Neurotransmitters and Other Factors Underlying Hypothalamic Mechanisms for Feeding

R. D. MYERS and T. F. LEE Departments of Psychiatry and Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27514 U.S.A.

A brief overview will be presented of the current status of putative neurotrans­mitters in their mediation of the diencephalic mechanisms subserving feeding and satiety. Special emphasis will be given over to illustrative evidence of species continuity for the noradrenergic pathways involved in feeding. For example, norepinephrine given i.c.v. in the cat enhances its normal intake offood which is attenuated by phentolamine.

212 ABSTRACTS

Recent observations will be considered which deal with the possible modulation of monoaminergic activity by certain peptides present in the CNS that influence the feeding response. These include the unique central actions of CCK and anorexigenic peptide on satiety, hunger and weight control. To illustrate, CCK perfused within the hypothalamus can enhance or suppress the release of norepinephrine depending on the anatomical site and the feeding status of the animal. Finally, new findings will be described on the central role of Ca 2 + ions and calmodulin as they relate to feeding and the set-point mechanism for body weight regulation. Calmodulin given centrally not only evokes feeding in the satiated cat but also augments the normal daily amount of food consumed. The specificity of this protein's action is shown by blockade with i.c.v. calcineurin or EGTA, but not troponin C.

Supported in part by USNSF Grant BNS-78-24491.

Bone Appetite of Phosphate Deficient Cattle

J. F. NELSON, J. R. BLAIR-WEST and D. A. DENTON Howard Florey Institute, University of Melbourne, Parkville, Victoria 3052, Australia

Osteophagia in cattle and other large ruminants, both wild and domestic, has been recognized for centuries in phosphate-deficient regions of the world. This behaviour has now been studied under laboratory conditions. We have carried out experiments using penned cows made phosphate deficient by dietary phosphate restriction plus the loss of phosphate from a parotid fistula. After phosphate deficiency over several months (plasma [P04 ] fell from 2 to 0·7 mM) bone appetite was tested by offering for the first time, a choice of rib bones or models of ribs made from plastic, plaster of Paris or wood. The only object picked up and chewed was the rib bone and this was done by all animals. In a second test the cows were offered a cafeteria of crushed old bone, crushed new bone, NaH2 P04 , CaHP04 , CaS04 and CaC03 . All animals took old or new crushed bone avidly but showed little or no interest in the other components, apparently identifying bone by smell. Phosphate-replete cows did not display any bone eating behaviour. Bone eating was suppressed by i.v. infusion of 100-300 mmol of sodium phosphate over 1-2'5h, this raised plasma [P04 ] to >2mM. Bone appetite reappeared about 2 h after the infusion ended when plasma [PO 4] had fallen to 1 mM. If similar amounts of sodium phosphate were infused in 15 min bone appetite was not immediately suppressed but interest gradually disappeared during the next 15-20 min. The results indicate that the appetite is innate and specific and that increasing extracellular [P04 ] accesses, over about 30 min, the CNS centres subserving the behavioural expression of phosphate deficiency.

Validation of the Ischymetric Hypothesis (IH)

S. NICOLAfDIS and P. EVEN College de France, 75231 Paris, France

Studies of the physiological mechanism offeeding distinguish the states of hunger, of satiety and the transitional, preabsorptive satiation which ends the meal and is substituted by the intermeal intervals satiety. These states are due to neurophysiological mechanisms sensing the 'depletion-repletion' fluctuations and transducing them

PHYSIOLOGY OF FOOD AND FLUID INTAKE 213

into the appropriate negative feed-back messages. New data on the stimulus as well as on its neuronal receptors will be reported. This stimulus is ischymetric (from WXWJ

= power) (W= Elt) or rate of energy production (EP). The ischymetric hypothesis proposes that hunger and satiety are generated at the level of specialized receptor cells sensing their own power production and transducing it into electrical and/or chemical message leading to arousal and hunger (S. Nicolaidis. Proceedings of the IU PS X, 122-23, New Delhi, 1974). This EP via ATP is supplied by metabolites originating from glucides, lipids and amino acids. Using an indirect computerized calorimetric system we have been able to measure instantaneously the power production of the non­locomotor cells of the animal, in spite of its free movements. This ischymetric rate designated "Metabolisme de Fond" (MF) decreased, first slowly and finally abruptly, before a meal was triggered. Satiation occurred on the zenith of MF which afterwards progressively reached the plateau level characterizing the state of satiety and sleep. These correlations are not fortuitous but causal, since experimental manipulation upwards or downwards of MF resulted in the predictable effect on feeding.

Light-Dark Rhythms of Food and Water Intake in Bulbectomized Rats: Effect of Muricide

N. A NICOLOV', O. C. IKONOMOV and A G. STOYNEV Departments of 'Pathophysiology and Physiology, Medical Academy, Sofia 1431, Bulgaria

Light-dark (LID) rhythms of food intake (FI) and water intake (WI) in five bulbectomized mouse-killing and in four sham-operated male Wistar rats were studied. Bulbectomy did not change the 24-h amounts or the L/D distribution ofthe FI and WI. Up to five mice were offered to each rat either in the L or D phase. In the D phase (D­muricide) rats killed five mice in all cases, while in the L phase (L-muricide) only 3·6 ± 0·5 mice were killed. Despite this difference both L- and D-muricide significantly suppressed the 24-h FI without changing the 24-h WI. The decrease of 24-h FI was due to a reduction of FI during the D phase.

It was concluded that (i) mouse-killing behaviour demonstrates a diurnal rhythm, and (ii) in both Land D phases muricide exerts a suppressive effect on 24-h food intake, but not on water intake.

The Effect of Gastrointestinal and Pancreatic (GEP) Hormones and Some Fatty Acids on the Discharge Rate of Vagal Hepatic Afferents

A NIIJIMA and A FUKUDA Department of Physiology, Niigata University School of Medicine, Niigata, 951 Japan

Afferent discharges were recorded from filaments dissected from the hepatic branch of the vagus nerve in the rat. Experiments were conducted in vivo or in isolated and perfused liver preparations with vagus nerves. Injections of insulin, 3-deoxytetronic acid into the portal vein increased the discharge rate, while glucagon, CCK-PZ, 2-deoxytetronic acid decreased it. The results suggest that GEP hormones and tested fatty acids which appear in the blood after starvation may modulate appetite and body functions through the hepatic vagal afferents.

214 ABSTRACTS

Nigral Unit Activity During Bar-Press Feeding Behaviour in the Monkey and Modulation by the Infusion of Glucose

H. NISHINO, T. ONO, M. FUKUDA, K. SASAKI and K. MURAMOTO Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-01, Japan

To investigate the role of the substantia nigra (SN) in the initiation and execution of the feeding behavior, unit activity ofSN neurons during bar-press feeding behavior was recorded and its modification by i. v. infused glucose was studied. Of 261 neurons tested, 16 (6%) responded in the discrimination stage non-specifically at the sight of food or non-food. In the bar-press and ingestion stages 102 (39%) and 100 (38%) responded, respectively. The majority of neurons seemed to be related strictly to motor function since the same response occurred when movement was elicited by any kind of food or non-food. These responses seemed to be coupled with motor execution but not with motor initiation since activity changes appeared with, but never before movement. Upon increasing blood glucose level (800 mg/kg i.v.) ingestion responses were weakened and spontaneous firing decreased while the responses related strictly to movement did not change at all. The data suggest two kinds of neurons, one coupled to feeding motor execution and the other to sensory integration in which responses are modulated by blood glucose level.

Adrenergic Antagonist and Preabsorptive Satiation

M. G. OCEGUERA, F. DE LA CRUZ, G. CHAM BERT and M. RUSSEK Department of Physiology, ENCB-IPN, Mexico, D.F. Mexico 11340

There is evidence that hepatic adrenaline participates in preabsorptive satiation (PS), so adrenergic antagonists should decrease PS and increase meal size. Reserpine (R) has been used in clinics to increase appetite in anorectic children. In the present study it was confirmed that R increases the amount ingested during the first hour of darkness in rats on an inverted night-day cycle, without increasing the amount eaten in 24 h. This endured for several days and was interpreted as an increase in meal size compensated by a decreased meal frequency. Guanetidine, a cathecolamine depleter that does not enter the brain produces the same as R, showing that the effect is peripheral. Dichloroisoproterenol, an inhibitor of adrenergic beta receptors produces an even greater and more prolonged effect, perhaps due to the irreversable blocking of these receptors. The observed effects are interpreted as an interference with the hepatic glycogenolysis elicited in normal circumstances by adrenaline from hepatic chromaffin cells.

Water Balance in Pregnant and Lactating Goats

K. OLSSON, K. DAHLBORN, S. BENLAMLIH and F. FYHRQVIST Department of Animal Physiology, Swedish University or Agricultural Sciences, Uppsala, Sweden and Minerva Institute, Helsinki, Finland

Water balance was studied in the same goats during pregnancy, lactation and anestrus. All goats increased their water intake during pregnancy. The individual differences were large and some goats drank more than five times as much during

PHYSIOLOGY OF FOOD AND FLUID INTAKE 215

pregnancy as during anestrus. Water intake during lactation was generally correlated to dry matter intake and milk production, but some lactating goats drank excessive amount of water. Urine volume was related to the amount of water consumed. Hence, urine osmolality was low during pregnancy and increased towards anestral values during lactation. Water deprivation caused elevated urine osmolality and decreased urine flow. Plasma osmolality and vasopressin concentration increased most rapidly and to the highest level in lactating animals, to somewhat less extent in pregnant goats, whereas comparatively smaller responses were seen during anestrus. The anti-diuretic response to vasopressin was reduced during pregnancy, and pregnant goats excreted a water load more rapidly than lactating or anestral animals. During intravenous infusions of hypertonic NaCI, the goats drank more water during pregnancy than during lactation or anestrus. The results indicate that the thirst threshold is lowered during pregnancy and in some animals also during lactation. Determinations of plasma renin activity and experiments involving the use of captopril suggest that increased activity ofthe renin-angiotensin system may contribute to the lowered thirst threshold and to the maintenance of arterial blood pressure in pregnant and lactating goats.

Chemosensitive Neurons in the Nucleus Tractus Solitarius (NTS)

Y. OOMURA and Y. MIZUNO Department of Physiology, Kyushu University, Fukuoka 812, Japan

Evidence indicated glucose responding neurons in the NTS, so 162 neurons were tested in brain slices containing the NTS. A statistically significant number (p < 0·05) of glucose-sensitive (GS) neurons were observed in that region. In the caudal region, 25 (28%) GS, 7 (8%) glucoreceptor (GR), and 57 non responsive neurons (28%) were noted among 89 cells tested. Of 73 cells tested in the rostral part, only a few responded-8 (11%) GS and 4 (5%) GR. Differences in the left and right side populations were not statistically significant in either the rostral or the caudal parts.

From anatomical and electrophysiological evidence the NTS is a relay point in the glucose analysis pathway, and serves as a caudal counterpart to the more rostral hypothalamus. The NTS is close to ventricle IV as the LHA is close to ventricle III, so the NTS could consolidate peripheral information, including the presence of hepatic, pancreatic, and intestinal glucose or insulin with intra ventricle or plasma levels and send the summarized information to the LHA which then executes similar functions in concurrence with the frontal and association areas of the cortex. Feeding related chemicals could affect the regulation offood intake through these other chemosensitive systems in conjunction with hypothalamic chemosensitive neurons. Also, since the NTS sends axons to the dorsal motor nucleus of the vagus, chemical information processing leading to peripheral control of insulin secretion could also occur.

Changes in Cerebrospinal Fluid Na and its Effects on Na and Water Homeostasis in the Na-replete rat

P. OSBORNE, R. S. WEISINGER and D. A. DENTON Howard Florey Institute of Experimental Physiology & Medicine, University of Melbourne, Parkville, Victoria 3052, Australia

It has recently been shown that alteration of cerebrospinal fluid [NaJ provokes changes in Na homeostasis in sheep. The present experiments evaluated the effect of

216 ABSTRACTS

altering CSF [Na] on both water and Na homeostasis in the Na-replete rat. Male Sprague-Dawley rats (250-450 g body wt) had continuous access to water and I-h access to 0·5 M NaCI solution. Under experimental conditions, a 4-h intraventricular (i.v.t.) infusion (10 or 38 pi/h) was begun 3-h prior to Na access. The solutions infused were 0·7 M mannitol-CSF (N = 9) or 0·5 M NaCI-CSF (N = 9). In sheep, the former infusion decreases the [Na] and increases the osmolality while the latter infusion increases both the [Na] and osmolality of CSF. The results indicated that both infusions caused a marked diuresis and natriuresis and that neither infusion caused any change in Na intake. The infusion of hypertonic NaCI-CSF caused an increase in water intake. These results suggest that both Na and osmoreceptors contribute to the various aspects of Na and water homeostasis. However, there is no evidence, at present, that altering CSF [Na] has any effect on Na intake in the Na-replete rat.

Dehydration-induced Thirst and Changes in ECF Volume in the Sheep

R. G. PARK, D.A. DENTON, M.J. MCKINLEY, B. A. SCOGGINS,J. B. SIMPSON, E. TARJAN and R. S. WEISINGER Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3052, Australia

We have examined the contribution of extracellular fluid volume (ECFV) to dehydration-induced thirst in sheep (body wt 32-42 kg). ECFV (bromide space), plasma volume (PV) (serum albumin space), water intake and body weight loss were measured before and after two days water deprivation. ECFV fell by 1020± 150ml (mean ± SEM, N = 4), PV did not significantly change, and body weight decreased by 2·6 ± 0·3 kg (N = 5). Water intake during the first hour of access was 2·52±0·361 (N = 5). Under experimental conditions the same animals were deprived of water for two days, then infused with 800-1200ml of 200mM NaCI i.v. at 40ml/min, 3h prior to water access, in order to replace estimated ECFV loss. The high infusate [Na] was necessary to minimize decreases in plasma [Na] caused by the ensuing natriuresis. At the time of water presentation, plasma protein concentration was decreased, showing expansion of plasma volume, and plasma [NaJ fell from 151 ± 1 to 148 ±2mM (normal = 145 mM). Body weight loss was 2·5 ±0'4 kg. Water intake during the first hour of access was 2·06 ±0·331, which was 22% less than the control water intake. This reduction may have been partially caused by reduced plasma [NaJ and osmolality. These preliminary data suggest that hypovolemia is not a major stimulus for thirst in dehydrated sheep.

Innate Recognition of a Salty Taste and Central Gustatory Damage

R. A. PAULUS, R. ENG and J. SCHULKIN University of Pennsylvania, Philadelphia, PA 19104, US.A.

There is a well-known phenomenon described in the literature of comparative psychology that is also evident in everyday life-incidentally learning something at one time, and then exploiting that knowledge at another time. How might this phenomenon be relevant to brain research?

PHYSIOLOGY OF FOOD AND FLUID INTAKE 217

Rats given the experience of merely tasting saline before receiving lesions in the thalamic taste relay have been shown to be protected from the usual lesion-induced deficits in salt appetite (Ahern et al., Journal of Comparative and Physiological Psychology, 92, 544-554, 1978). However, in the Ahern et al. study, the preoperative saline taste experience and the post-operative salt appetite test occurred with the saline in identical locations. In this study, the location of the saline during post-operative testing was varied from the location during preoperative training for some rats, and kept the same for others. The protective effect occurred predominantly when the location of the saline was the same.

This protective effect may be due to place-learning, in part, since it is known that rats remember tasting saline in a particular place and then return there when is a state of sodium need (Krieckhaus, Journal of Comparitive and Physiological Psychology, 73, 117- 123,1970). We interpret the results in support of an earlier hypothesis suggested by Krieckhaus (1970), since our results suggest that the preoperative tasting of saline triggers an innate recognition of its significance, thereby permitting a learned association between taste and place.

Effects of Systemic or Intracerebroventricular Naloxone Injection on Basal and 2-deoxy-D-glucose (2-DG)-induced Ingestive Behaviors

L. PENICAUD and D. A. THOMPSON Endocrine and Metabolism Unit, University of Rochester, Rochester, NY 14603, U.S.A.

In order to examine the role and site of action of opiates on both hunger, thirst, food and water intakes in rats after short-term food deprivation (2 h) alone or combined with 2-DG induced glucoprivic stress, naloxone was given to rats either in the jugular vein or in the lateral ventricle. Both basal and 2-DG-induced food and water intakes were reduced by naloxone injected either centrally or peripherally. Latencies to eat and drink were used as measures of hunger and thirst. Only intracerebroventricular injection of naloxone significantly reduced 2-DG-induced but not basal hunger. 2-DG­induced thirst was reduced by systemic injection of naloxone. These results suggest a central site of action of naloxone on both food and water intakes even if the peripheral effects cannot be totally ruled out. Our findings indicate a contral role of opiates in the 2-DG-induced hunger, otherwise the reduction of food intake cannot be imputed to the reduction of hunger but could be due to augmented satiety, perhaps associated with retardation of gastric emptying during opiate receptor blockade.

Angiotensin-induced Thirst in Man: Physiology or Pharmacology?

P. A. PHILLIPS, B. J. ROLLS and J. G. G. LEDINGHAM Departments of Physiology, Psychology and Medicine. University of Oxford, Oxford, u.K.

Angiotensin II (All) is a potent dipsogenic stimulus in almost all species so far tested, and has been implicated in the thirst of malignant and renovascular hypertension in man. However, its physiological role in thirst is controversial. We therefore investigated whether it could be involved in physiological thirst in man by infusing All-amide (Hypertensin, CIBA) IV into ten fluid-replete, healthy, informed.

218 ABSTRACTS

volunteer young men at mildly pressor doses (2- 16ng/kg/min for 60min) and compared the plasma All levels needed to induce thirst in these fluid replete subjects with the plasma All levels after 24-h water deprivation, 0-45 M hypertonic saline infusion and during ad libitum water access. We found that four of the ten subjects responded to the All infusion with significantly greater water intakes compared to the single blind isotonic saline control infusion. The dose required to produce this dipsogenic effect (16 ng/kg/min) has been found by other workers to be at the threshold for angiotensin-induced thirst in other species. The plasma All levels achieved during the infusion and associated with thirst were very much higher than those occurring during the other physiological manipulations. These results suggest that All is dipsogenic in some men, however the plasma levels needed are far in excess of those occurring under physiological conditions, and that without other synergistic factors (e.g., hypovolaemia, cellular dehydration) the dipsogenic effect of All in man is pharmacological rather than physiological.

Regulation of CSF Insulin

D. PORTE, JR., D. G. BASKIN, D. M. DORSA, D. P. FIGLEWICZ, D. L. WEST, L. J. STEIN, H. IKEDA and S. C. WOODS Departments of Medicine and Psychology, University of Washington, and VA Medical Center, Seattle, WA 98108, US.A.

We have suggested that circulating insulin provides a signal from the adipose tissue to the central nervous system regarding the size of the adipose mass. We have hypothesized that circulating immunoreactive insulin (IRI) has access to the brain via the cerebrospinal fluid (CSF). This hypothesis was originally based upon the finding that insulin is normally found within the cerebrospinal fluid in dogs and that its concentration can be influenced by the infusion of exogenous insulin. Three new pieces of data support this hypothesis. 1. Insulin levels have been measured in baboon CSF drawn from chronic omnyan reservoirs connected to Pudenz catheters permanently implanted into the fourth cerebral ventrical or cisterna magna. In adolescent baboons CSF insulin averages 3 JiU/ml and ranges from 5- 15% of simultaneously measured plasma values. Over a 7-h period when food was available CSF IRI gradually increases after a delay of 45 min. Peak CSF IRI doubled at the end of the day and were three to five times basal with plasma insulin two to ten times basal. A 5-h intravenous infusion of glucose plus exogenous insulin further increases plasma insulin and CSF insulin with maximum values in CSF of 20- 30 JiV/ml. Peak CSF and plasma IRI values during feeding and i. v. infusion are highly correlated (r = + 0·92). Thus, elevation of plasma IRI by either exogenous infusion or endogenous secretion produces a proportionate rise in CSF IRI. 2. CSF IRI has now been detected in Wistar, Zucker lean, and Zucker fatty rats. Mean basal levels are 5-10% of plasma values but are three-fold higher in fatty compared with control Wistar or lean heterozygotes. In free feeding animals there is a statistically significant increase in both plasma and CSF. Therefore, endogenous CSF insulin appears to increase with feeding in rats as it does in baboons and is elevated in obese animals. 3. Infusion of insulin into the CSF via cannulas implanted into the third ventricle of Zucker fatty and Zucker lean heterozygotes via Alzet mini pumps for 14 days leads to suppression of food intake and reduction of body weight in the lean animals only. Therefore, insulin provided into CSF suppresses food intake in lean rats, but not in the Zucker model of obesity.

PHYSIOLOGY OF FOOD AND FLUID INTAKE

Regulatory Drinking Following Graded Hemorrhage in Dogs

D. J. RAMSAY, T. N. THRASHER and C. H. METZLER

219

Department of Physiology, University of California, San Francisco, CA 94143, US.A.

Reduction in venous return caused by graded constriction ofthe thoracic vena cava in dogs causes drinking. In the present series of studies, the effects of reductions in total circulating blood volume brought about by hemorrhage were studied. The experiments were carried out on a population of 19 dogs. On the morning of an experiment, the dogs were brought up to the laboratory, and allowed to settle down in a loose canvas sling for a period of 30 min. Blood was removed at 1·5 ml/kg/min, and volumes ranging from 10 to 35 ml/kg were withdrawn. Following completion of hemorrhage, the dogs were offered water and the volumes consumed over the 60 min measured. The dogs began drinking soon after access to water was allowed (mean latency 9 ± 3 min). Drinking increased in a dose-related manner up to the highest level of hemorrhage tested (Y= 0·25X - 1'3, where Y= water intake in ml/kg, X = volume blood withdrawn, ml/kg, r = 56, p < 0'001). The drinking was correlated with the fall in blood pressure associated with the hemorrhage (Y=0' 14X+1-4, where Y=water intake in ml/kg, X=fall in blood pressure, mm Hg, r= 61 , p<O·OOl). Although the general population of animals increased water intake over the whole range of hemorrhage, a small number (2) showed marked reductions in water intake at levels of hemorrhage greater than 25 ml/kg. These animals also showed inability to maintain their blood pressures, giving credence to the suggestion that blood pressures below a certain critical value impair the ability to drink. These data demonstrate that increased water intake in response to hypovolemia can be regulatory.

Supported by HL18862 and AM06704.

Caudal Hindbrain Participation in Controls of Ingestive Behavior

R. C. RITTER WO.I. Veterinary Medicine Program, University of Idaho, Moscow, ID, US.A. and Department of V. CAP. P. , Washington State University, Pullman, WA, US.A.

Recent evidence suggests that the hindbrain plays a potentially important role in the control of ingestive behavior. Work from our lab indicates that the receptor cells which mediate glucoprivic feeding are located in the hindbrain. In fact several investigators have observed that lesions of caudal hindbrain structures, the area postrema (AP) and adjacent nucleus of the solitary tract (NST), abolish glucoprivic feeding. However, such lesions also cause additional behavioral signs, including reduced body weight, overconsumption of highly palatable foods and enhanced responsiveness to angiotensin-induced thirst. Although the lesions which produce these signs all involve the AP and a portion of the adjacent NST, the individual alterations of behavior result from the damage to distinct neural systems. For example, intra-AP injection of capsaicin, a neurotoxin which destroys a specific population of sensory neurons, causes overconsumption of palatable foods without causing loss of body weight, enhanced drinking in response to angiotensin or loss of glucoprivic feeding. Although our recent data show that behavioral effects of thermal lesions to these areas do not simply represent loss of vagal afferent input, the components of the lesion syndrome can be individually reproduced by selective dam~ge to other

220 ABSTRACTS

connections of the AP and NST. The results suggest that the syndrome observed following physical damage to the AP and adjacent NST is the net effect of destruction of functionally distinct subsystems or connections of these structures.

Time of Day Effects of Dipsogens on Rat Water Intake and Urine Output

JENNY REDMAN and STUART ARMSTRONG Department of Psychology, La Trobe University, Bundoora, Victoria 3083, Australia

Rats housed in a light cycle composed of 12 h light and 12 h dark display daily rhythms in water intake and urine output. Both rhythms normally peak in the dark. Hormonal systems concerned with fluid regulation also fluctuate rhythmically throughout the 24-h period. It was therefore predicted that dipsogens acting on these hormonal systems would vary in potency with time of day. Dipsogens (angiotensin II, hypertonic saline and isoproterenol), were injected i.p. into male Long-Evans rats at four times during the 24-h period (early light, late light, early dark, late dark). Water intake and urine output in the 2-h period after injection were measured concomitantly. Water intake was significantly facilitated by angiotensin II in the late light compared to the early light. Hypertonic saline significantly increased water consumption in the early dark compared to early light and late dark. Urine excretion was increased by both dipsogens but output did not vary significantly with time of day. The increase in water intake induced by isoproterenol was similar at all four injection times. Isoproterenol was anti-diuretic in the light but induced increased urine output in the dark when compared to controls. The results of these experiments highlight the need to examine drug effects at a number of times during the 24-h period.

The Onset of Amino Acid Imbalance: An Operant Approach

QUINTON R. ROGERS, THOMAS CASTONGUAY and PHILIP M. B. LEUNG Food Intake Laboratory, University of California, Davis, CA 94616, U.S.A.

In order to establish the time course for the food intake depression of rats fed a threonine devoid diet 12 male Sprague-Dawley rats were trained to earn over 80% of their total daily intake of food during a 2-h session by manipulating a small lever within a standard, sound-attenuated testing chamber. Each rat was trained to earn its food (45 mg pellets of a low protein basal diet) according to a variable interval 40 sec schedule of reinforcement. After stable patterns of lever pressing were established for each rat they were placed in the testing chamber and rewarded for bar pressing with threonine-devoid diet pellets. Only one of the 12 rats failed to show serious disruption in bar-pressing performance during the initial2-h test session. Five of the rats stopped responding on the lever during that session. Of the remaining seven, six rats reduced their pellet acquisition rate to a small fraction oftheir normal (basal diet) rate. Six of the 12 rats showed severe disruption in operant response rates within the first 40 min of the first devoid diet session. Subsequent testing with these same animals after a two week recovery period showed that plasma threonine levels were decreased at the time disruption occurred, consistent with the hypothesis that changes in plasma amino acid concentration may mediate the food intake depression.

Supported in part by NIH Grants T32AM07355 and AM 13252.

PHYSIOLOGY OF FOOD AND FLUID INTAKE

Body Weight Regulation in Pregnancy and Lactation

B. J . ROLLS and P. M . VAN DUIJVENVOORDE University of Oxford, Department of Experimental Psychology, Oxford, u.K.

221

During pregnancy and lactation extreme changes in food intake, body weight and body fat occur. In pregnancy carcass fat is deposited, while during lactation both hyperphagia and fat mobilization promote milk production. We have determined the effect of pre-existing obesity and the type of diet available on body weight regulation during reproduction. Throughout pregnancy obese and lean rats were fed either chow or a cafeteria diet of palatable high energy foods and chow. The non-foetal weight gain in pregnancy was affected by the type of diet available but not by pre-existing obesity. Thus fat deposition in pregnancy is not regulated at a set level for sustaining lactation. In lactation, there is a regulatory utilization of body fat stores. Weight changes in lactation are inversely related to the non-foetal weight gain in pregnancy, weight after giving birth, and weight at mating. Obese rats are finicky in that they show an exaggerated weight loss when switched to chow in lactation compared to consumption of the cafeteria diet. The diet has a smaller effect on the weight changes of lean rats during lactation. Further evidence that the lactational weight change is regulated is that after a three day food restriction in mid-lactation both obese and lean rats were hyperphagic until they regained the lost weight. Their weights then continued to change as before restriction. The weight loss may depend on insulin levels or sensitivity since it is reversed by daily insulin injections. An understanding of why lactating rats can lose weight despite the availability of a palatable high energy diet could provide insight into ways to control body weight.

Functions of Hypothalamic and Extrahypothalamic Neurons in Feeding

E. T. ROLLS Department of Experimental Psychology, University of Oxford, Oxford, u.K.

There is a population of neurons in the lateral hypothalamus and substantia innominata which respond to the sight and/or taste of food if the monkey is hungry. To obtain evidence on how these neurons fit into the circuitry for ingestive behavior (Rolls, in Brain mechanisms of sensation Pp. 241- 269. New York: Wiley, 1981), their activity is being compared with that of neurons in other, connected, regions in the same feeding test situations in macaque monkeys, with the following results. 1. These neurons may receive their inputs via the pathway from the inferior temporal visual cortex, in which purely visual rather than motivation-related neuronal responses are found, via the amygdala, in which neurons are found which come to respond to visual stimuli partly on the basis of whether the stimuli signify food. 2. Some outputs of the basal forebrain feeding-related neurons are directed towards the cerebral cortex, and may by this route, as well as by descending pathways, influence the initiation of feeding. 3. The orbitofrontal cortex contains neurons which are involved in correcting feeding responses when these become inappropriate. 4. The striatum contains neurons which are involved in feeding by preparing the monkey to make a behavioral response, and other neurons which may be involved in well learned motor responses to stimuli which signify food.

222 ABSTRACTS

Acute and Chronic Effects on Water Balance by Forebrain Lesions in the Goat

M. RUNDGREN Department of Physiology, Karolinska institutet, 104 01 Stockholm, Sweden

Permanent adipsia was induced in two goats by lesions in the preoptic-septal region of the forebrain involving also the anterior part of the sub-fornical organ. The vasopressin (VP) secretory response to dehydration was blunted after lesioning, but the anti-diuretic responses to i.v. infusion of hypertonic (inf ht) NaCI and systemic hypotension (SH) were largely unaffected by the brain damage in both animals, and also to i.v. angiotensin II in one of the goats. Four weeks post-lesion, signs of inappropriate anti-diuresis evolved in one of the adipsic animals. In two other goats with unilateral lesions extending above the supraoptic nucleus, a similar defect in water excretion, without increased plasma VP levels, was observed seven days post-lesion. The ability to excrete a water load was then normalised. These animals reduced their daily water intake by roughly 30-40% after lesioning. A fifth animal, supplied with three electrodes in the anterior part of the septal region was lesioned in two subsequent sessions. On each occasion an acute water diuresis developed, during which preserved anti-diuretic responses to SH and i.v. inf ht NaCI were seen. No obvious dehydration was induced by the acute post-Iesioning water losses, since they were compensated for by drinking within 5 h. It is suggested that destruction, to a varying extent, of juxtaventricular sensors or afferents from such structures, involved in the cerebral control of water balance, may induce complete or partial absence of the urge to drink water, and that effects on VP secretion and water intake can be dissociated by such lesions.

Lateral Hypothalamic Unit Activity and Eating Behavior

K. SASAKI, T. ONO, H. NISHINO, M. FUKUDA, K. MURAMOTO and K. NAKAMURA Department of Physiology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-01, Japan

It has been repeatedly demonstrated that the lateral hypothalamic area (LHA) is important in control of feeding. Only a few electrophysiological studies, however, have analyzed relationships between LHA unit activity and real feeding behavior. To study such relationships, single unit activity was recorded from the LHA of freely moving rats during ad libitum feeding, during eating behavior after food deprivation, and after intraventricular injection of norepinephrine (NE) in satiated rats. Of 122 neurons tested during ad libitum feeding, firing rate changed (usually inhibitory) in 52% during access to food, picking up with tongue and chewing. In one-fourth of 47 neurons, activity depression during feeding episodes was greatest immediately after food deprivation and least in conditions of ad libitum feeding. Spontaneous unit activity was independent of deprivation duration. Of 47 neurons tested during intraventricular NE-induced feeding, spontaneous unit activity decreased in 12 and increased in three. Results suggest that LHA neurons are involved in ad libitum and intraventricular NE-induced feeding behavior and unit activity of some is modified by motivational state such as hunger or satiation.

PHYSIOLOGY OF FOOD AND FLUID INTAKE

Brain Cholecystokinin and Satiety in Fowls

C. J. SAVORY and M. J. GENTLE Poultry Research Centre, Roslin, Midlothian EH25 9PS, Scotland

223

This paper describes five experiments designed to test whether brain CCK acts as a satiety factor in fowls. (1) Twelve hens with intracerebroventricular (i.c.v) cannulae, and with access to food from 1000--1600 hrs each day, were injected i.c.v. at 1000 hrs on two days each week with 0·1 or 0·4 flg/kg CCK8 dissolved in 0'9% saline (0·2 flg/ fll), or equivalent volumes of saline. In the first 30 min after CCK injections food intake was reduced (p < 0'01) by 20% with 0·1 flg/kg and 31 % with 0·4 flg/kg, compared to that after saline injections. Birds were not unwell after injection. (2) In a similar experiment, 12 hens ate more (p < 0'05) in the first 15 min after i.c.v. injections of 4 and 20 nmol/kg of the CCK antagonist dibutyryl cyclic GMP than after injections of saline. Intake was increased by 11 % with food access from 1000-1600 hrs, and by 36% with ad libitum access. Neither increase was dose-related. (3) Blood glucose levels in 12 hens after i.c.v. injections of 0-4 flg/kg CCK8 did not differ from those after injections of saline, in either fed or fasted states. (4) I.c.v. injections of 0·5 flg/kg CCK8 had no effect on gizzard or duodenal motility in four hens fitted with strain gauge transducers. Two of these birds were drowsy after CCK injection. (5) Mean concentrations of CCK8 in different parts of the brain did not differ between 16 fed chicks and 16 chicks fasted for 24 hrs. Conclusion: satiety effects of i.c.v. CCK injections cannot be explained by hypergly­caemia or gastric inhibition, but may be associated with drowsiness. The GMP results support the idea of a central satiety role for CCK.

Alimentary Preoperative Experience and Lateral Hypothalamic Damage

J. SCHULKIN, G. WOLF and S. J. FLUHARTY University of Pennsylvania, Philadelphia, PA 19104, New York University, New York, NY 10003, and University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.

The hypothalamus has been thought to be involved in the system that organized motivated behavior. In a series of studies we have investigated the effects of various preoperative alimentary motivational experiences on salt appetite following lesions of the lateral hypothalamus. We find that the preoperative experience of a salt drive (DOCA furosemide) with or without the experience of reinforcement by salt ingestion, is sufficient to protect the animal against the usual deficit in regulatory salt intake that follows lateral hypothalamic lesions. In contrast in this study we report that the preoperative experience of merely tasting salt, without concomitant salt or thirst drive, does not have a protective effect. Preoperative thirst experience with water ingestion also does not seem to ha ".:-:: a protective effect on salt appetite, but it may protect against drinking deficits following the lesion. The results are discussed in the general context of recovery of brain function and mechanisms of preoperative immunization.

224 ABSTRACTS

Suppression of Sodium Appetite by Interference with the Action of Cerebral Angiotensin

JACOB SCHULTZ and ALAN N. EPSTEIN University of Pennsylvania, Philadelphia, PA 19104, U.S.A.

If a synergy of angiotensin (A) and aldosterone is the cause of sodium appetite (Epstein, Peptides, 3, 1983), then prevention of the action of endogenous angiotensin should suppress the appetite. This prediction was tested successfully in six adrenalectomized rats drinking excess volumes of 3% NaCl. Their appetites for salt were reduced by almost 90% by continuous overnight intracerebroventricular infusion (ci .c.v.) with doses of captopril (12 ng through 1·2 J.lg/hr) that were sufficient to block conversion to AI to AIl in the cerebral ventricles. Concurrent water intakes were unreliably, and only slightly (15%), reduced. Arousal of a DOCA-induced appetite (2-6 mg/day for four to six days) for 3% NaCI in the same animals was not reduced by identical ci.c.v. infusions of captopril.

These results encourage the proposal that the brain becomes hungry for the taste of salt as the result of the combined actions of angiotensin and aldosterone, and suggest that the action of angiotensin within the brain may be crucial for this synergy.

Supported by NINCDS 03469

Variations in Sodium and Pota~sium Intake Modify the Renal and Dipsogenic Responses to ACTH Administration in Sheep

B. A. SCOGGINS, J. P. COGHLAN, D. A. DENTON, T. J. HUMPHERY, E. H. MILLS and J. A. WHITWORTH Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3052, Australia

On an intake Na 100mmol/d, K 250mmol/d ACTH (20J.lg/kg/day for five days) increases water intake, urine volume (UV), GFR, ERPF and blood pressure. Na excretion falls for 24-48 h then returns to pre ACTH levels. Plasma [K] fell without change in K excretion. Reduction ofNa intake to < 2 or 10 mmol/d had no effect on the ACTH-induced rise in UV or water intake. The fall in plasma [K] was blunted. Reduction of K intake to < 20 mmol/d blocked ACTH-induced increases in UV and water intake but plasma [K] fell. On an intake of < 2 mmol/d Na and < 20 mmol/d K UV and water intake increased with ACTH without hypokalemia. On K intake of 800-1000mmol/d ACTH effects UVand water intake were also blunted. ACTH raised blood pressure on all regimes and there was no simple relationship between Na and/or K intake and rises in blood pressure. These studies show that the level ofNa and/or K intake modify the dipsogenic and diuretic responses to ACTH administration in sheep.

Neural Connections of the Rat Area Postrema

ROBERT E. SHAPIRO and RICHARD R. MISELIS Laboratories of Anatomy, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, U.S.A.

The area postrema (AP), a circumventricular organ in the midline dorsal medulla, has been implicated in the control of a wide variety of ingestive behaviors including

PHYSIOLOGY OF FOOD AND FLUID INTAKE 225

food intake, salt appetite, and the thirst of hypovolemia and angiotensin II. We investigated the neural"connectivity of the AP using the anatomical tracers WGA-HRP conjugate or cholera toxin-HRP conjugate. We pressure-injected via micropipette small volumes of tracer (60 nl or less, appro x 3% conc. wt/vol) into AP or in controls the underlying nucleus of the solitary tract (NTS) and subsequently processed the whole brain according to the TMB protocol of Mesulam. We found efferent projections, (1) within the NTS extending both caudally and rostrally to Obex, and (2) a prominent efferent tract passing from AP ventrolaterally to reach the region of nucleus ambiguus. These fibers then turned rostrally to ascend within the A 1 and A5 catecholaminergic cell column and then rose within the lateral lemniscus to terminate in a pair of very heavy discrete fields in the lateral parabrachial nucleus (PBL) and more lightly in the midbrain periaqueductal gray and the mesencephalic nucleus ofY. Prominent afferent connections to AP include a bilateral horizontally-oriented ring of hypothalamic neurons extending caudally from and including the lateral parvocellular subnucleus of the para ventricular nucleus. These cells appear to encapsulate the parvocellular hypothalamic nucleus in an interlocking plexus of TMB-Iabelled dendrites. Sparce numbers of labelled neurons were observed rostral to the efferent field in PBL and in caudal NTS as well.

Supported by grants GM27739 and USPHS5T32GM07517.

Properties of a So-called Anorexigenic Peptide

T. SHIRAISHI', A. SIMPSONt, N. SHIMIZUt, and Y. OOMURAt , Department of Physiology, Tokai University Medical School, Bohseidai, Isehara 259-11, t Department of Physiology, Showa University School of Medicine, Tokyo and t Department of Physiology, Kyushu University Faculty of Medicine, Fukuoka, Japan

A tripeptide, pyroGlu-His-GlyOH, which was isolated from the urine of anorexia nervosa patients and purified, was reported in 1978 to be anorexigenic in either its natural or its synthesized form. Two separate attempts to replicate the earlier dramatic results were reported as unsuccessful in 1979 and 1980. We report here a further attempt at replication plus results of some electrophysiological measurements.

Subcutaneous injections totalling 10 to 40 ltg/kg over five days did not change feeding, body weight, or gastric acid secretion (GAS) of rats. Doses of 30 Jig/kg suppressed GAS-induced by insulin (80 U /kg, s.c.) and electrical activity in the gastric branch of the vagal nerve.

When applied ionophoretically in the hypothalamus it suppressed the activity of lateral hypothalamic glucose-sensitive neurons of either the gastric type (GAS induced by stimulation) or the non-gastric type, but did not affect non-glucose-sensitive neurons. In the ventromedial nucleus of the hypothalamus, activity of glucoreceptor neurons (excited by glucose) was Jacilitated, but non-glucoreceptors were not affected.

It was concluded that peripheral application of this peptide has no effect on feeding through any peripheral route, but it does affect activity of central neurons which are known to control feeding. The effects of central application ofthis peptide remain to be examined.

226 ABSTRACTS

A Comparative Evaluation of D-Fenfluramine and DL-Fenfluramine on Subjective Hunger, Food Intake, Psycho­motor Function and Side Effects in Normal Human Subjects

TREVOR SILVERSTONE and GLENYSS SMITH Medical College of Sf. Bartholomew's Hospital, London, U. K.

Eighteen normal subjects (4M, 14F) reported at 0830 hrs following an overnight fast on six occasions at least one week apart. At 0900 hrs they received one ofthe following: 30mg o-fenfluramine (o-FF), 40mg o-FF, 60mg o-FF, 30mg oL-fenfluramine (OL­FF), 60 mg OL-FF or matching placebo. Visual analogue scales for junger, satiety, arousal and mood and a side effects questionnaire were completed before medication and at 60 min intervals for the next 8 h. A standard preweighed platter meal was presented for 30 min and calorie intake measured 4 h post-drug. Pulse, blood pressure and pupil diameter were recorded and blood samples taken for drug plasma levels at 0, 1, 2, 4 and 8 h. Psychomotor function (digit substitution and digit elimination) was tested and salivary flow measured at 0, 1, 3 and 6 h.

Subjective hunger and food intake were significantly reduced by 0- and OL-FF with o-FF having twice the anorectic potency of oL-FF such that 30mg o-FF was equipotent to 60 mg OL-FF but caused fewer side effects.

These findings have important clinical implications for the drug treatment of obesity.

Changes of Plasma and Cerebrospinal Fluid (CSF) Osmolality with Relevance to Thirst Stimulation and Water Intake (WI)

CH. SIMON-OPPERMANN, E. SIMON and E. SZCZEPANSKA-SADOWSKA Max-Planck-Institut, D-6350 Bad Nauheim, F.R.G. and Department of Applied Physiology, School of Medicine, 00-730 Warsaw, Poland

Central osmoreceptive control of WI may be a function of either plasma (P osm) or CSF (CSFosm) osmolality. We compared changes of osmolality in these compartments following 24-h dehydration, subsequent rehydration by drinking water, and i.v. infusion of 5% NaCI solution to elicit osmotic thirst. The experiments were performed on conscious dogs implanted with a device enabling the collection of CSF from the third ventricle. Dehydration increased Posm from 295·9± 1·0 to 317·1 ±2'8mOsm/kg and CSFosm from 294'0±0'9 to 318·2±2·9mOsm/kg (N=14, M±SE). WI of the dehydrated dogs was correlated with both Posm (r = 0'72, 2p<0'005) and with CSFosm (r =0·71, 2p <0·005) found before rehydration. Rehydration decreased Posm more rapidly than CSFosm, the latter being higher by 8'6± l'4mOsm/kg (2P<0'001) at 90 min after the onset of drinking. Significant correlations were found between WI and the decrements on Posm (r = 0'92, 2p<0'001) and in CSFosm (r=0'88, 2P<0·00l) caused by drinking. At the moment of threshold stimulation of thirst induced by i.v. infusion of hyperosmotic saline. CSFosm had increased 9·8±2·3mOsm/kg less than Posm (2P<0·001). The results reveal a significant delay in equilibration ofCSFosm with Posm during rapid changes of body fluid osmolality. Similar feedback mechanisms, though with different time constants, appear to operate between CSF osm and WI as between Posm and WI.

PHYSIOLOGY OF FOOD AND FLUID INTAKE

The Effect of Naloxone on Intragastric Ethanol Self-administration

J. D. SINDEN, P. MARFAING-JALLAT and J. LE MAGNEN

227

Neurophysiologie Sensoriel/e et Comportementale, Col/ege de France, 75231 Paris, France

The acute effect of 1·25 and 2·50 mg/kg naloxone was tested in a group of male Wi star rats readily self-administering 10% w/v ethanol intragastrically following 12 days of forced enthanol intoxication. Compared to saline pretreatment, naloxone did not alter 24-h intakes of food, water or ethanol. However both doses strongly and significantly inhibited lever pressing for ethanol during 2 h following pretreatment. This is interpreted as a performance deficit perhaps resulting from a short-term withdrawalproducing effect of naloxone. The higher dose of naloxone significantly increased lever pressing for ethanol 2-4 h after pretreatment. This increase resembles an extinction effect produced by substituting saline for the ethanol reward. The results suggest that naloxone does have post-absorptive ethanol reward-inhibiting properties.

Adrenalectomy Reduces Caloric and Fat Intake and Body Weight Gain in Genetically Obese Zucker Rats (fafa)

J . S. STERN, T. W. CASTONGUAY, S. BROWN, K. STANHOPE and G. A. BRAY Department of Nutrition, University of California, Davis, CA 95616 and Division of Diabetes, University of S. California, Los Angeles, CA 90033, U.S.A.

Male and female, obese and lean Zucker rats were adrenalectomized (ADX) at 10 weeks of age. At 30 weeks of age body masses of ADX, obese, male rats fed a high carbohydrate diet were comparable to that of control lean rats (475 vs. 469 g respectively) and less than that of control obese rats (662 g). Adipose cell sizes of ADX obese rats in gonadal (GON) and retroperitoneal (RP) sites were comparable to those of control lean rats. While subcutaneous adipose cell size from ADX obese rats was smaller than obese controls, it was still larger than that from control lean rats. Lipoprotein lipase activity (LPL)/cell was predictably elevated in control obese rats vs lean rats. However, no differences between lean control and obese ADX LPL activity/cell were found in either GON or RP sites. In a second study female, ll-week­old obese and lean rats were provided access to three macronutrient sources: a protein source, a carbohydrate source and a liquid fat source. ADX severely reduced the caloric intake of only obese rats and the reduction in caloric intake was principally due to a significant reduction in the intake of fat. These studies emphasize the importance of the adrenal gland in excessive weight gain, elevated adipose LPL activity, fat cell hypertrophy and dietary fat selection observed in obese Zucker rats.

Supported in part by NIH gra nts AM 18899 and AM 31988.

Effects of Anti-depressants on Body Weight, Intake and Carbohydrate Craving

L. H. STORLlEN, F. M. HIGSON, R. M. GLEESON, D. M. ATRENS and G. A. SMYTHE Garvan Institute, St. Vincent's Hospital, Darlinghurst, New South Wales 2010 and Psychology Department, Sydney University, New South Wales 2006, Australia

Major negative side-effects reported for anti-depressant drugs in humans are excess weight gain and carbohydrate craving. Few studies have attempted to establish

228 ABSTRACTS

whether weight gain or carbohydrate craving are side-effects of anti-depressants in animals. The aim of the present study was to establish an animal model for investigation of these phenomena.

Three experiments investigated the effects oflithium (40 mg/kg LiCI), amitriptyline (2'5 mg/kg), mianserin (2'5 mg/kg) and saline administration (15-20 days, one subcu­taneous injection/day) on body weight, food intake and fluid intake (water, 0'6% saccharin and 24% sucrose). A vail able in Experiment I were food cubes; in Experiment 2 cubes, saccharin and sucrose; and in Experiment 3 cubes and saccharin. Lithium administration resulted in a marked increase in weight gain but only if both sucrose and saccharin were available. Saccharin intake was always increased with lithium as was total caloric intake with sucrose available. Amitriptyline induced a sweetness craving; however, weight gain was somewhat depressed with just cubes available and only normalized by the additional availability of sucrose and saccharin. With amitriptyline, total caloric intake was never different from controls. Mianserin had no effect on any measure.

The results demonstrate the usefulness of the rat as a model for the energy balance perturbations of some anti-depressant drugs and focus on carbohydrates as a major factor contributing to excess weight gain.

Biological Bases of Sodium Appetite in Rats

EDWARD M. STRICKER Department of Psychology, University of Pittsburgh Pittsburgh PA 15260, US.A.

Rats usually develop sodium appetite 5 h after subcutaneous injection of polyethy­lene glycol (PEG) solution. However, recent experiments indicate that sodium appetite appears withip. 30--60 min if the rats had been maintained on sodium-deficient (NaD) diet instead of Purina Chow for two to four days previously. Sodium appetite was no longer potentiated by pretreatment maintenance on NaD diet when the hypersecretion of aldosterone after PEG administration was prevented by hypophysectomy. How­ever, sodium appetite still appeared 5 h after PEG treatment when secretion of aldosterone was abolished by adrenalectomy in rats maintained on DOCA therapy. These and other observations suggest the possibility that relatively small amounts of mineralocorticoids have an important permissive effect in mediating sodium appetite during hypovolemia. Because elevated levels of angiotensin II (All) paralleled the appearance of NaCI consumption after PEG treatment, it seemed reasonable to consider a possible role for All in sodium appetite. In this regard, NaCI consumption was enhanced in PEG-treated rats when All was produced in unusually large amounts in the brain, owing to the systematic administration of captopril. This latter effect occurred even when drinking water was withheld and plasma sodium concentrations were markedly elevated. Collectively, these findings suggest that the normal secretion of aldosterone in rats after PEG treatment might permit physiological amounts of All to be effective in stimulating sodium appetite.

Gastrin and Cholecystokinin in Regulation of Food Intake

K. V. SUDAKOV, K. V. ANOKHIN and I. Yu. ORBACHEVSKAYA P. K. Anokhin Institute of Normal Physiology, US.S.R. Academy of Medical Sciences, Moscow 103009, US.S.R.

The study shows that neuropeptides cholecystokinin (CCK) and pentagastrin (G) may regulate food intake through central mechanisms. Injection of G(20 mkg/kg s.c.)

PHYSIOLOGY OF FOOD AND FLUID INTAKE 229

caused feeding in satiated rabbits. It was accompanied by appearance of bursting activity in neurons of lateral hypothalamus. Interval pattern of this activity was the same as in hungry animals. Microionophoresis of G to the neurons of lateral hypothalamus and sensomotor cortex in unrestrained satiated rabbits evoked the same interval pattern of neuronal activity suggesting that G induces feeding behavior acting directly on central neurons. Both peripheral and i.c.v. administration of CCK-8 (5; 15 mkg/kg and 10; lOOng/kg respectively) increased dopamine (DA) turnover in the same areas. CCK antagonized locomotor hyperactivity induced by amphetamine, showing that its action or the DA system is an inhibitory one. These results support the idea that CCK coexisting with DA in the neurons of mesolimbic system acts as a neuromodulator of DA function connected with food reward.

Differential Effects of Light Intensity and Periodicity on Food Intake in Normal and Brain Lesioned Rats

ANITA SYLVAN, RICHARD M. GOLD and LYCIA A. CARTER Department of Psychology, University of Massachusetts, Amherst, MA 01003, U.S.A.

The effects of light cyclicity and light intensity were investigated in normal, parasagittal hypothalamic knife cut, and SCN lesioned rats. Under 24-h (LD 12 : 12) and 3-h (LD 1·5: 1'5) light: dark cycles, female rats consumed most of their food in the dark. Knife cuts only transiently disrupted these feeding patterns. SCN lesions permanently blocked circadian feeding. Finally, reduced light intensity obliterated any existing light-dark differences for animals tested on the 3-h but not the 24-h schedule. Thus, light appears to affect feeding through more than one neural mechanism, and obesifying parasagittal knife cuts do not permanently disrupt circadian feeding rhythms.

Plasma and Cerebrospinal Fluid Vasopressin: Relation to Water Intake

E. SZCZEPANSKA-SADOWSKA, CH. SIMON-OPPERMANN and D. GRAY Department of Applied Physiology, School of Medicine, 00-7300 Warsaw, Poland and Max-Planck-Institut, 0-6350 Bad Nauheim, F.R.G.

The relations between the central and the peripheral release of vasopressin (A VP) and water intake (WI) were examined in seven conscious dogs chronically implanted with a device for the collection of the cerebrospinal fluid (CSF) from the anterior part of the third ventricle. CSF-AVP and plasma A VP (P-AVP) concentrations were measured by radioimmunoassay. Blood and CSF samples were collected simulta­neously under conditions of normal hydration, after threshold stimulation of thirst by i.v. infusion of 5% NaCI solution and after 24-h dehydration and subsequent rehydration by drinking of water. Resting values ofP-AVP and CSF-AVP in normally hydrated dogs were 2·7±0·2 and 25·1±3·6pg/ml, respectively (N=14, M±SE). Threshold osmotic stimulation of thirst was associated with significant increases in P-A VP and CSF -A VP. Dehydration caused a significant increase in P-A VP and a non­significant rise of CSF -A VP. WI was significantly correlated with both P A VP (r = O' 72, 2p < 0'005) and -CSF -A VP (r = 0'6\, 2P < 0'05) found before rehydration. Rehydration

230 ABSTRACTS

caused an immediate non-osmotically mediated lowering of P-A VP and a subsequent osmotically-mediated lowering of both P-A VP and CSF-A VP. The final decrements in P-AVP caused by drinking were correlated with WI (r=O'77, 2p<0·005). The results suggest that mutual relationships exist between the central and the peripheral A VP release and WI.

Salt and Water Intake of Wild Rabbits Following Intracerebro­ventricular Infusion of Angiotensin II

E. TARJAN, D. J. DENTON and J. F. NELSON Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Victoria 3052, Australia

Wild rabbits (Oryctolagus cuniculus), caught in a low salt area were offered ad libitum food, water and electrolyte solutions. Intracerebroventricular (i.c.v.) infusion of angiotensin II (All) 10 ng/h, for five days caused a progressive increase in sodium intake and urinary sodium excretion which was significantly different from control from the fourth day of infusion, and lead to a positive sodium balance following the cessation of infusion. Water intake was not different from control throughout the study, but urine volume was higher on the fourth day of infusion, and was increased following the cessa tion of All infusion. I.c.v. infusion of All, 50 ng/h, for 22 h did not alter the water intake, but resulted in a negative sodium balance and a decrease in plasma sodium concentration. I.c.t.v. infusion of All, 500 ng/h, for 22 h caused a decrease in water intake, an increase in urinary sodium excretion, followed by an increase in sodium intake after the infusion of All was stopped. Intraperitoneal injection of All 100,ug/kg, did not cause water drinking, nor did intraperitoneal injection of hog renin 30 mU /kg. Wild rabbits seem to differ from the most investigated rodent species, the laboratory rat, in the sensitivity and reaction to All in both regulatory systems subserving thirst and sodium homeostasis.

Effects of Lesions of the Organum Vasculosum Laminae Terminalis (OVLT) on Drinking in Response to Cellular and Extracellular Stimuli in the Dog

T. N. THRASHER and D. J. RAMSAY University of California, San Francisco, CA 94143, U.S.A.

This report summarizes recent observations of the effects oflesions of the OVLT in drinking in dogs. A total of six dogs met the criteria of 95% destruction of the OVL T without significant damage to surrounding periventricular tissue. Destruction of the OVLT elevated the threshold increase in plasma osmolality required to elicit drinking to hypertonic NaCI (0'3 mM/kg/min, i.v.) from 8 ± 2 to 23 ± 2 mosmol/kg and reduced intake from 43 ± 4 to 15 ± 3 ml/kg. Before destruction of the OVL T, angiotensin II (All, 20 pM/kg/min, i. v.) caused drinking in all six dogs (4 ± 1 ml/kg in 30 min). After the lesion only one of six dogs drank in response to All. The volume of water drunk in I-h following 24-h water deprivation was similar before (36 ± 7 ml/kg) and after (43 ± 9 ml/kg) lesioning the OVL T. However, plasma osmolality increased more in response to dehydration after destruction of the OVLT (16 ± 2 mosmol/kg compared

PHYSIOLOGY OF FOOD AND FLUID INTAKE 231

to 9 ± 2 mosmol/kg before). Therefore, water intake was inappropriately small relative to the deficit.

Preliminary data in three dogs suggest that drinking in response to hemorrhage (20 ml/kg) was not affected by lesioning the OVLT (10'5 ml/kg before vs. 8·9 ml/kg after). These data are consistent with the hypothesis that the OVLT is an osmoreceptor site in the dog. We suggest that, in the absence of normal osmoregulatory input from the OVLT, All is not an effective dipsogen in the dog. Finally, preliminary evidence suggests that drinking in response to deficits in extracellular fluid volume are not affected by destruction of the OVL T.

Supported by HL-OII06 and AM06704.

Effect of Naloxone on Schedule-induced Behaviours

M. WALLACE, G. L. WILLIS and G. SINGER Brain-Behaviour Research Institute, La Trobe University, Bundoora, Victoria 3083, Australia

There are various reports that the narcotic antagonist, naloxone reduced schedule induced (S-I) water intake. In this experiment the effects of i.p. injections of naloxone on schedule-induced drinking were compared with sal butanol, deprivation and hypotonic saline induced drinking in the white rat.

It was found that naloxone reduced water intake in all conditions, but higher doses of naloxone were necessary to effect a significant reduction in S-I-drinking.

Intravenous Insulin Self-administration in Normal and Insulin­Dependent Rats: A New Animal Model

E. K. WALLS and G. SINGER Department of Psychology, La Trobe University, Bundoora, Victoria 3083, Australia

A previous report of intravenous insulin self-administration (louhaneau & Le Magnen, Physiological Behaviour 20, 1978, 739-747) demonstrated that insulin intake was stable and related to food intake on normal rats. However, when these rats were made diabetic insulin intake became unstable.

A vena caval catheter exteriorized into an acrylic skull cap provided chronic vascular access for connection to the infusion delivery devices in all animals. Rapid acquisition and stable maintenance of insulin intake were not obtained when normal rats were given discontinuous (l2-h daily) access to a single operant lever delivering

intravenous insulin. A continuous access paradigm with two operant levers, one delivering 45 mg food pellets, the other delivering a 5 sec intravenous pulse of regular bovine insulin (0'025 U/infusion) was found to promote rapid acquisition and stable insulin intake in normal and streptozotocin-induced diabeti.c rats. The pattern of insulin intake indicated that peak insulin intake correlates with peak anabolic demand. The success of this approach in diabetic rats is contingent upon previous experience with the food operant lever and a relatively stable metabolic state resulting from subcutaneous Lente insulin therapy prior to insulin self-administration testing. The capacity for learning this adaptive regulatory behavior in diabetic animals suggests a new animal model with potential for a variety of physiological and behavioral investigations.

232 ABSTRACTS

Regulatory Insulin Self-administration in the Streptozoticin­induced Diabetic Rat

E. K. WALLS" G. SINGER" and T. B. WISHARTt • Department of Psychology, La Trobe University, Bundoora, Victoria 3083, Australia and t University of Saskatchewan, Saskatoon, S7N OWO, Canada

A series of experiments employing normal rats with permanent intravenous catheters revealed that rapid acquisition and stable maintenance of insulin intake were accomplished when access to food pellets and intravenous infusions of regular bovine insulin were made contingent upon depression of two separate operant levers.

In rats made diabetic with streptozoticin (55 mg/Kg, i.v.) which were maintained on one fixed daily subcutaneous injection of long-acting insulin (0·0, 1·0, 2·0, and 4·0 U frat), it was observed that voluntary insulin intake varied inversely with the subcutaneous dose oflong-acting insulin. At all doses, food (66-77%) and insulin intake (59-70%) was predominantly restricted to the 12 h of dark and significant positive correlations were observed between mean hourly rates of food and insulin intake. A significant decrease in voluntary insulin intake was observed when diabetic rats were given unrestricted opportunity to exercise in running wheels. A comparison of voluntary insulin intake of diabetic rats maintained on three different diets containing normal (52%), high (62%), and low (31%) carbohydrate revealed a small elevation in insulin intake with the high carbohydrate diet, whereas insulin intake on the low carbohydrate diet was markedly reduced. It is suggested that the diabetic rat learns to utilize cues from behaviorally produced metabolic changes to adjust subsequent behavior, achieving a more optimal metabolic state.

Blockade of Angiotensin II Production in the Brain and Suppression of Sodium Appetite in the Rat

M. WEISS and A. N. EPSTEIN Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, U.S.A.

We have previously ascribed (Epstein, Peptides, 1982, 3) the arousal of sodium appetite to the increased levels of the hormones angiotensin II (All) and aldosterone which result from sodium depletion. We have tested this idea by blocking the formation of All in the brain with infusion of captopril (Squibb), which inhibits the conversion of AI to All. Sodium depletion was produced by furosemide (10 mg, s.c.) plus sodium­deficient diet in rats fitted with intracerebroventricular (i.c.v.) cannulae. They were infused overnight with captopril (1·2 ng, 12 ng, 120 ng, 1·2 jig, or 12 jig/h) or its vehicle during the entire 18-h depletion period (when sodium was unavailable) and during a subsequent 2-h sodium appetite test when 3% NaCI was offered. This was followed by confirmation of the AI to All blockade by failure of the dipsogenic response to pulse i.c.v. AI, followed by drinking to pulse i.c.v. All.

Sodium appetite, but not overnight water intake, was reduced in a dose-related manner by the 12 ng, 120 ng, and 1·2 jig/h doses. The highest dose (12 jig) had a non­specific suppressive effect on overnight water intake. The lowest dose (1·2 ng) failed to block AI to AIl conversion and did not block the salt appetite. The 1·2 jig/h dose did not alter sodium excretion.

These results support our hypothesis that All in the brain has a role in the arousal of the sodium appetite of sodium depletion.

PHYSIOLOGY OF FOOD AND FLUID INTAKE 233

Neuroleptic-like Anorexia Produced by an Extra-cerebral DA Antagonist G. L. WILLIS and G. C. SMITH Monash University Department of Psychological Medicine, Prince Henry's Hospital, Melbourne, Victoria 3084, Australia

The effects of the DA receptor antagonists metoclopramide and pimozide on food and water intake in male Sprague-Dawley rats were compared to those of domperi­done, which does not cross the blood-brain barrier, in an attempt to determine whether any extracerebral DA receptors participate in neuroleptic-induced anorexia. While metoclopramide caused only minor changes in food and water intake at the doses employed both pimozide and domperidone caused a significant reduction in food intake and water consumption and 4-h after injection during a 4-h intake test. These results support the hypothesis that the nigrostriatal system may not be the system principally involved in the neuroleptic induced anorexia which occurs after the administration of these drugs (Wise et ai., Science, 1978,201,262-264.).

Another look at Oral and Post-ingestional Factors Involved in Satiating Salt Appetite

G. WOLF Department of Psychology, New York University, New York, NY 10012, U.S.A.

Earlier studies on short-term satiation of salt appetite seemed to indicate that post­ingestional factors do not play a significant role. The present studies compared satiating effects of saline intubated or ingested under highly controlled conditions of sodium deprivation and appetite testing. The results indicated that there are three separate processes involved in the satiation of salt appetite: (a) an immediate effect of oral (presumably gustatory) stimulation; (b) a rapidly acting post-ingestional effect presumably involving gastrointestinal receptors, and (c) a long latency effect develop­ing over several hours and possibly involving shifts in the slowly exchangeable pool of body sodium.

Intraventricular Insulin Enhances the Satiating Effect of Cholecystokinin

STEPHEN C. WOODS, HITOSHI IKEDA, LESLIE J. STEIN, DIANNE P. FIGLEWICZ, DAVID B. WEST and DANIEL PORTE, JR. University of Washington, Seattle, WA 98915, U.S.A.

We have shown that the intraventricular (i.v.t.) infusion of insulin into baboons reduced food intake and body weight (100 f.1 U /kg/day reduces food intake by 41 %). We also showed that the efficacy of cholecystokinin (CCK) to reduce 30-min meal size was greater when baboons had recently eaten and when CSF insulin is elevated. To test the hypothesis that CSF insulin interacts with the satiating effect ofCCK, we administered a minimally effective dose of CCK to baboons in the absence or presence of a chronic i.v.t. infusion of insulin. Each baboon initially received several doses (0'5-4 f.1g/kg) of CCK intravenously as a 5-min infusion prior to food presentation. A probe dose was chosen which reduced 30-min food intake by 10% or less. Synthetic CSF was then infused i.v.t. at a rate of 5 ml/day. The probe dose of CCK was then repeated with and without the addition of insulin (100 f.1g/kg/day) to the synthetic CSF. Insulin had a

234 ABSTRACTS

variable effect on daily food intake, causing significant reduction in some baboons and no change in others. However, in every animal, the suppression of 30-min meal size by the probe dose of CCK was greatly increased by the addition of insulin to the CSF infusate. In most animals, the suppression went from 10% or less to over 90%, and the change was significant by paired t-test. These data suggest that insulin acting at the brain interacts with short-term satiety factors to alter meal size.

Electrophysiological Characteristics of Supraoptic Neurons in Rat Hypothalamic Slice Preparation

H. YAMASHITA and K. INENAGA Department of Physiology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu, 807, Japan

It has been well known that neurosecretory neurons in the supraoptic nucleus (SON) control body water balance by secreting vasopressin from their axon terminals in the neurohypophysis. Control mechanisms and stimuli for vasopressin release have been well documented. However, basic characteristics of SON neurons have not yet been fully studied by intracellular recordings. Intracellular recordings were made from neurons in the SON of rat hypothalamic slice preparations. The resting membrane potentials were of - 50-- 70 m V; the amplitudes of the action potentials were of 50-90 m V; the membrane resistances were of 70-180 Mohms. Spontaneous firing of the intracellularly recorded potentials had a random firing pattern and a phasic firing pattern superimposed on slow periodic depolarization. Most of the phasic firing neurons were identified immunocytochemically as vasopressin containing neurons. Intracellular stimulation of the neurons produced action potentials with a duration of about 4 msec. Longer duration action potentials were elicited in a low sodium bathing medium or in a normal bathing medium containing tetrodotoxin. The longer duration action potentials disappeared by application of EGTA or cobalt in the bathing medium. The present study shows an evidence of calcium spikes and reveals basic characteristics of neurosecretory neurons in the SON of the rat hypothalamus.

Water-Mineral Metabolism in Man under Hypokinesia

Y. G. ZORBAS and N. I. ABRATOV Hypokinetic Physiology Laboratory, European Institute of Environmental Cybernetics, Athens 514, Greece

The effect of hypokinesia (HK) on fluid-electrolyte balance was evaluated in eight physically healthy men in the age group 18-22 years. For the reproduction of HK all men were subjected to 120 days of rigorous bedrest regime. Then the following parameters were determined: daily amount of water consumed and eliminated in urine, alterations in body weight, water content in the blood, plasma volume, electrolyte composition of the blood and urine, rate of glomerular filtration and renal blood flow, osmotic concentration of urine and blood, sodium and potassium content in the blood serum and urine. The parameters under study exhibited changes in a wave-like pattern and they were reverted back to normal following exposure to hypokinesia. It was concluded that the observed alterations of water-mineral metabolism in man under the influence of hypokinetic conditions were adaptatjonal in nature.