Amphetamine, Chlorpromazine and Clonidine Effects on Self-Stimulation in Caudate or Hypothalamus of the Squirrel Monkey
JOHN SPENCER t AND ALVIN REVZIN
Department o f Psychiatry and Behavioral Sciences, University o f Oklahoma Itealth Sciences Center, Oklahoma City, OK
and
Aviation Toxicology Laboratory, Civil A eromedical Institute, Federal Aviation Administration. Oklahoma OLv, OK 73125
(Received 15 October 1975)
SPENCER, J. AND A. REVZIN. Amphetamine, chlorpromazine and clonidine ~Lffects on self-sthnulation b~ caudate or hypothalamus of the squirrel monkey. PIIARMAC. BIOCHEM. BEHAV. 5(2) 149-156, 1976. - In 2 separate groups of squirrel monkeys and within 3 animals low rates of intracranial self-stimulation (ICSS) elicited from caudate or lateral hypothalamic brain sites were increased by as much as 200% above control levels by amphetamine (0.5 mg/kg). Thresholds for responding were decreased by 50%. Increasing the drug dose from 2 to 10 mg/kg produced response inhibition at both brain sites. The duration of inhibitory action of amphetamine (2.0 mg/kg) on ICSS from the medial forebrain bundle (MFB) area of the lateral hypothalamus was 6 hr. At caudate sites ICSS did not occur until 48 hr had elapsed. A 10 mg/kg dose of amphetamine produced a duration of action of 36 hr in the MFB and 84 hr in the caudate. Chlorpromazine (CPZ) doses of 0.5 and 1.0 mg/kg decreased caudate ICSS significantly more than lateral hypothalamic ICSS. At 1.0 mg/kg the duration of action of CPZ was 6 hr at lateral hypothalamic brain sites and 24 hr at caudate sites. At a 2.0 m,g/kg CPZ dose the duration of action was 12 hr in the MFB and 36 hr in the caudate. A dose of 0.10 mg/kg of clonidine blocked high rates of MFB ICSS while within the same animal caudate ICSS was much less affected. Higher doses (0.25 mg/kg) sedated the animal and ICSS was equally inhibited at both sites. These findings, using ICSS as a behavioral measure, suggest that the effects of amphetamine and CPZ involve not only hypothalamic structures but more anterior telenccphalic sites as well. The prolonged actions of amphetamine and CPZ on caudate ICSS suggest that drugs acting, in part. on dopamine containing neurons will interfere with certain caudate mediated behavior. Further, since hypothalamic but not caudate ICSS sites are more dose sensitive to drugs that selcctivcly act on NE containing neurons, other amines in addition to NE may play a role in the support of 1CSS.
I N T R A C R A N I A L self-st imulat ion (ICSS) has been used as a behavioral t echnique to assess the effects o f the psycho- mimet ic drugs on operan t response rate [ 13, 17, 18, 24, 26, 28, 29 ] , neurophysiological correlates of behavior [19[ , and biochemical correlates of behavior [2, 20, 2 5 , 2 7 1 . This l i terature has recent ly been reviewed by German and Bowden [8] . Generally, sys temic adminis t ra t ion of stim- ulant drugs such as a m p h e t a m i n e increases the rate of responding for hypo tha lamic ICSS in rats [17, 24, 26] . If the tranquil izing drug ch lo rp romaz ine (CPZ) is given, rates of responding are reduced [13, 18, 19]. A positive correlat ion appears to exist be tween the inhibi tory effects of CPZ on hypo tha lamic ICSS and single unit activity
within the hypo tha l amus [19] , suggesting a hypotha lamic locus of act ion for CPZ.
Because amphe tamine and CPZ can influence the release and re-uptake of norep inephr ine (NE), [3,91, it has been suggested [261 that the central site o f act ion for these drugs is within areas such as the hypo tha lamus , that contain large amoun t s of this amine. Po ten t ia t ion of hypotha lamic ICSS by amphe tamine can be significantly reduced if the animal has been pre t rea ted with drugs (e.g., disulf iram) that inhibit the enzymat i c synthesis o f NE. When l-nor- epinephr ine is then injected intraventr icularly, ICSS is restored in 15 min and by 75 min the facilitating effect of amphe tamine is again observed. Thus, amp he t amine ' s
~'l'his research was supported in part by Federal Aviation Administration task AM-A-TOX-22 and hy USPHS Grant 5t01 M[t 10322 O~iological Sciences Training Grant) from the Department of Psychiatry and Behavioral Sciences, University of Oklahoma Ilealth Sciences Center, Oklahoma City, OK. The authors would like to thank Mr. Bill Henderson for his assistance with tile histology. Reprint requests should bc sent to John Spencer, Ph.D., Behavioral Sciences Department, Naval Medical Research Institute, Bethesda, MD 20014.
149
150 SPENCI 'R AND REVZIN
s t imula t ing ac t ion on behav ior may involve, in part , a l te ra t ions in NE release, a l t hough disulf i ram may not be a pure inh ib i to r of NE synthes is [ 6 ] .
It has also been shown tha t low doses of a m p h e t a m i n e induce greater faci l i ta t ion in rate of ICSS from the locus coeruleus (LC) than from the h y p o t h a l a m u s [22 ] . The densi ty of NE-con ta in ing neurons is qui te high in the LC, and this region is one origin for a no rcp inephr ine rg ic pro jec t ion pa thway with very widespread d iencephal ic and te lenccphal ic c o n n e c t i o n s [ 15] . This pa thway forms a par t of the medial forebra in bund le (MFB), a diffuse f iber t ract which projects in to and th rough the h y p o t h a l a m u s [ 1 0 ] . The f inding that LC ICSS is very sensit ive to a m p h e t a m i n e is not surpris ing assuming thai the drug affects NE t ransmiss ion in the brain and tha t NE is a necessary med ia to r of ICSS.
O the r data have been presented t h o u g h which show tha t the pharmacolog ica l and behaviora l ac t ions of a m p h e t a m i n e or CPZ may not be expl icable purely in te rms of NE. A release not only of NE but ace ty lcho l ine (ACH), d o p a m i n e (DA) and g a m m a a m i n o b u t y r i c acid ( G A B A ) c o m m o n l y occurs t h r o u g h o u t much of the brain including the caudate nucleus, which has high p r o p o r t i o n s of DA, when the p sychomime t i c drugs are given [ I, 11, 16]. Fu r the r , ICSS can occur at the caudate or subs tan t i a nigra [12 ,17] and evidence has been presented which shows a m p h e t a m i n e can inf luence rates of ICSS from e i ther the h y p o t h a l a m u s or subs tan t ia nigra [17] thus suggesting some in te rac t ion be tween brain sites, amine c o n t e n t and ICSS. Based on these findings, it would appear tha t drug effects on several n e u r o t r a n s m i t t e r sys tems can inf luence rates of r e spond ing for ICSS a l though the relative role of these systems in the media t ion of ICSS remains to be clarified.
The present set of expe r i m en t s analyze the dose effects and dura t ion of ac t ion of a m p h e t a m i n e and CPZ on ICSS in the squirrel m o n k e y , a species in which no in fo rma t ion is available regarding I( 'SS and drug act ion. Two sites have been used to elicit ICSS, the head of the cauda te and the h y p o t h a l a n m s . A third drug, c lonidine , was also used in the present s tudy to assess its effect on ICSS elicited from caudate and h y p o t h a l a m i c sites. This drug is t h o u g h t to act pr incipal ly on NE con ta in ing neurons [ 1 4 ] . If several brain pa thways for ICSS do in fact exist , then those tha t con ta in large a m o u n t s of NE (e.g., h y p o t h a l a m u s ) would be predic ted to be more dose suscept ible to c lonid ine ' s effects than those con ta in ing large a m o u n t s of DA (e.g., caudate) .
M I ' T H O I )
Animals and Housing Conditions
Twelve hea l thy , adul t squirrel m o n k e y s were used in the present exper iments . Body weights were be tween 600 and 800 g. Each animal was housed in an individual cage I l V-" x 1!~ x 2 ft). All animals were fed s tandard squirrel m o n k e y chow with supp lemen t s of fruit and vi tamins. The cages were watered and cleaned daily. The room t em pe r a tu r e was cons tan t at 72<'F. Light cycle was 12 hr on and 12 hr off.
Surger.v
Each animal was initially anes the t i zed with pento- barbi to l (25 mg/kg) and placed in a s te reo tax ic ins t rument . The c ran ium was exposed and stainless steel wire e lec l rode pairs (0.25 mm dia.) insulated except for the t ips (0 .50 mm} were bi lateral ly implan ted via small holes drilled in the
skull. Coord ina te s used for implan t ing at the head of lhe caudate were tAP 15.0. I. 2.5. V 17.(I mm) and for the lateral h y p o t h a l a m u s tAP 8.5 11.0, L 0.5 1.5, V I I . 0 mm) [7] . The leads f rom the e lec t rodes were connec ted to an EL( 'O plug and the ent i re assembly was e m b e d d e d in denta l repair acrylic. The incision was then closed and the animal was pe rmi t t ed to recover f rom the surgery. . -ks a p recau t ionary measure against infect ion, bicillin (0.25 co) was given in t ramuscu la r ly one day prior to surgery and several days thereaf ter . The recovery period was 2 weeks in dura t ion . There was no evidence of pos topera t ive in- fections.
Testing Apparatus
The expe r imen t was c o n d u c t e d in a vent i la ted sound- p roof chambe r (3~5x 3 x 4 ft, Lehigh Valley). The animals were held in a conven t iona l two-pla te res t ra int chair. A lever was m o u n t e d in a vertical pos i t ion in f ront of and 5 cm above tile animal. The required response was to reach out and up to grasp the lever and pull.
Each lever pull act ivated a mic roswi tch that triggered a Tek t ron ix waveform genera to r systena. Rec tangula r t rains of pulses (100 c/see, pnlse wid th 0.2 msec) were delivered via a m u l t i c o n d u c t o r cable. l ' h e cur ren t in tens i ty , pulse width, and waveform were mon i to r ed on a dual -beam oscil loscope. To provide a c o n t i n u o u s record of the animal ' s response, a cumula t ive recorder (xnodel ('R21), Scientific P r o t o t y p e ) was also ~,ctivated by each lever pull. Min imum in te r s t imulus interval was (,30 reset. For the a m p h e t a m i n e admin i s t r a t i on studies, s t imulus parameters w e r e s e l e c t e d that p roduced low response rates ( 15.. 20/ra in) , while for the CPZ and c lonidine e x p e r n n e n t s maximal rates of r esponding (above 5 0 / m i n i were used.
Dose Response ,4 nal.vsis
/tbsolute rate..<,ix animals were selected that had stable response rates to s t imula t ion of the head of the caudate ; (~ o the r animals were chosen with s table response rates from the hypo tha l amus . Three of these 12 subjects had positive sites in bo th the h y p o t h a l a m u s and the caudate .
Each animal was placed in the c h a m b e r and allowed to self-s t imulate for 15 rain on the CRF schedule. Saline was then injected into a small marshmal low and given to lhc animal. Recording was then con t inued for a fu r the r 60 rain.
Fol lowing 3 days of saline con t ro l recording, e i ther d - a m p h e t a m i n e su lpha te (0 .25, 0.50. 1.0. 2.0, or 10.0 mg/kg) dissolved in saline, or c h l o r p r o m a z m c hyd roch lo r ide ( ( 'PZI was given in a r andomized order in place of saline. Because of drug solubi l i ty problems , the 10.0 mg/kg dose of a m p h e t a m i n e was given in te rpe r i tonea l ly tIP) instead of orally. ( ' on t ro l s tudies showed tha t the stress of the IP inject ions did not al ter rates of ICSS. All animals were food deprived for I 2 hr pr ior to the test session so as to facil i tale absorp t ion of the drug. The m i n i m u m interval be tween successive drug admin i s t r a t ions was 2 weeks. Later in the exper iments , dosages of 0.05, 0.10, or 0.25 mg.'kg of c lonidine were given, as previously described.
77zreshold changes. A separate analysis for changes in the threshold values of s t imulus curren! was pe r fo rmed fol- lowing a m p h e t a m i n e admin i s t ra t ion . A current in tens i ly that p roduced a s table low rate. (15 20 responses per minu te [ r e s p / m i n ] ) ,,,,'as used as the s tar l ing point and 50 mic roamperc s tepwise decreases in the cur ren t were con- t inued unti l the aqinml s topped responding. A m p h e t a m i n e
DRUG EFFECTS ON SELF-STIMULATION BEHAVIOR 151
dosages used were 0.25, 0.50, and 1.0 mg/kg, and the drug adminis t ra t ion procedure was as described above.
Duration analysis. Analysis of dura t ion of drug effects followed the above procedures initially, l [owever , 3 hr af ter drug adminis t ra t ion the animal was placed back in the exper imenta l chamber and retes tcd for 1 hr. This same procedure was repeated at 6, 12, and 24 hr pos tdrug and then every 24 hr until the animal 's response rate had re turned to its original baseline level. Each time the animal was placed in the chamber a marshmal low was given, fol lowing the procedure described above. For those animals with e lec t rodes that yielded self-st imulat ion from both sites, each site was investigated separately for 40 rain; the order of the site tested was counte rba lanced , and if one site elicited ICSS but the o ther did not , the analysis for that particular dose of drug was replicated twice.
IIistology
All animals were sacrificed with an overdose of Nem- butal at the end of the exper iment . Final e lec t rode track verification was made by examining cross sect ions of the brain, cut frozen, at 100 micron sect ion thickness. The sect ions were then m o u n t e d on slides and stained with cresyl violet acetate to facilitate localizing final e lect rode track penet ra t ion .
REStJLIS
Amphetamine
Rate o f response. Statistical analysis was pe r fo rmed on the rate of response per rain (drug/saline ratio x 100). In all tests the max imum F value needed at the appropr ia te probabi l i ty (p) level (conservative or negative biased test, Winer, 1'-)73) was used. A 2 x 5 analysis of variance with repeated measures on the last factor [30] demons t r a t ed a
significant main effect for brain site (F(1 ,10) = 8.90, p<O.05) and for drug dose ( F ( 1 , 1 0 ) = 4 7 . 3 1 , p < 0 . 0 1 ) . The interact ion be tween brain sites and drug dose was not significant (F ( I , IO) = 4 . 8 1 , p > 0 . 0 5 ) . As dose of drug was increased from 0.25 to 0.50 mg/kg, the ratio of responding (low rate) was significantly increased at both caudate and hypotha lamic sites and at 1.0 mg/kg, hypo tha lamic sites only. Doses higher than 1.0 mg/kg significantly decreased rate of ICSS from bo th sites, (Fig. IA).
An individual cumulative response record for one animal is presented in Fig. 2. A m p h e t a m i n e increased the response rate from bo th caudate and hypo tha lamic sites at dosages of 0.5 mg/kg and at hypotha lamic sites at 1.0 mg/kg. Rate of ICSS from the caudate showed various periods of no responding fol lowed by increases in responding at 1.0 mg/kg. Five animals showed various periods of rate in- creases or decreases while one animal showed a steady reduct ion in rate of response. The higher s tandard error of the mean for the caudate brain site at 1.0 mg/kg (Fig. 1) reflects the larger group variation in mean percent change in rate of ICSS.
Current threshold. Significant decreases in current threshold were obta ined at 0.50 mg/kg of amphe tamine at both brain sites and at 1.0 mg/kg in the hypo tha lamus (Fig. 1B) (F(1 ,20) = 40.00, p<O.01). Statistical analysis of changes in threshold for responding at caudate sites was not made at 1.0 mg/kg since there were periods of both rate increases and rate inhibit ion.
Duration o f action. The durat ion of act ion of amphel - amine on rate of ICSS is presented in Fig. 1C. Since the unit of measure {hours to return to baseline) was arbitrarily set in the exper imenta l design, a planned compar ison using nonparamet r ic ranking procedures was used [23] . At doses of 2.0 and 10.0 mg/kg animals with e lect rodes implanted at the head of caudate did not self-st imulate for 48 hr at the 2.0 mg/kg dose and 84 hr at the 10 mg/kg dose. This
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F:IG. I. (A) Dose-response curve for amphetamine effects on rate of sell:stimulation from head of caudate (N = 6) or medial forebrain bundle (MFB) in the lateral hypothalamus (N = 6) of squirrel monkeys. Vertical bar represents standard error of the mean. (B) Dose-response curve for amphetamine effects on current threshold needed to elicit self-stimulation at caudate (N = 6) or MFB (N = 6). Vertical bar represents standard error of the mean. (C) Duration of action of amphetamine on rate of self-stimulation from head of caudate (N = 6) or the MFB (N =
6) brain sites. Vertical bar represents standard error of the mean.
152 SPENCER AND RFIVZIN
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HG. 2. Cumulative response record for one squirrel monkey that received dosages of 0.5 or 1.0 mg]kg of amphetamine. Brain site stimulated was the medial forebrain bundle (MFB) in the lateral
hypolhalamus or the head of the caudate.
behavioral du ra t ion of ac t ion was s ignif icant ly longer than for those animals tha t had e lect rodes imp lan ted wi th in the lateral h y p o t h a l a m u s (U = 0, p < 0 . 0 0 1 ) . A l though e i the r low or high rates of ICSS could be elicited wi th in the lateral h y p o t h a l a m u s by 36 hr, 3 of the animals tha t had e lectrodes implan ted at b o t h sites would not con t inue to respond if the active e lec t rode was swi tched to the caudate . Between 8 4 - 9 6 hr all animals responded when e i ther site was s t imula ted . The 10.0 mg/kg dose p roduced anorex ia in all animals lasting for 24 hr. A n o t h e r c o m m o n behaviora l sequela previously repor ted in cats [21] was tha t the
monkeys appeared to sit quie t ly in thei r home cages and fixate in to space.
Chlorpromazine (CPZ) Rate o f response. A 2 x 4 analysis of variance (brain site
and drug dose), wi th repeated measures on the last fac tor [30] revealed a s ignif icant in t e rac t ion be tween drug dose and brain site (F (1 ,10) = 9.68, p < 0 . 0 5 ) . After simple effects analysis was made, b e t w e e n - t r e a t m e n t to ta ls analysis was done using the Scheff6 test.
Doses of CPZ at 0 .50 and 1.0 mg/kg produced a significant decrease in rate of r esponding when the head of the caudate was s t imula ted . These d i f ferences in caudate ICSS were also s ignif icant ly d i f fe ren t f rom ICSS elicited from the h y p o t h a l a m u s . Drug doses of 2.0 mg/kg produced a s ignif icant decrease in responding at b o t h sites (Fig. 3A).
The du ra t ion of ac t ion of CPZ is presented in Fig. 3B. Again a n o n p a r a m e t r i c analysis based on signed ranks was pe r fo rmed [23}. At doses of 1.0 and 2.0 mg/kg self- s t imula t ion was inh ib i ted for longer periods of t ime from the caudate sites than f rom h y p o t h a l a m i c sites (U = O, p<0 .001 : U = 1, p < 0 . 0 0 1 ) . These d i f ferences were observed bo th be tween groups and wi th in 3 animals.
An individual cumula t ive record from an animal in which b o t h the cauda te and the h y p o t h a l a m u s suppor ted se l f -s t imulat ion is presented in Fig. 4. At a dose of 0.5 mg/kg CPZ b locked cauda te se l f -s t imula t ion for 6 hr while rate of ICSS from the h y p o t h a l a m u s was not changed. At 1.0 mg/kg the cauda te site again failed to suppor t I( 'SS and rate of ICSS f rom the h y p o t h a l a m u s was reduced. At 2.0 mg/kg b o t h sites failed to suppor t ICSS for 12 hr (MFB) and 36 hr (caudate) .
Clonidine
Low doses of c lonidine (0.05 mg/kg) did not change rate of r esponding for s t imula t ion at e i ther cauda te or hypo- tha lamic sites. A dose of 0 .10 mg/kg of c lonidine reduced h y p o t h a l a m i c ICSS for 30- -45 rain. Rate of ICSS elicited from the head of the caudate was not cons i s ten t ly reduced (Fig. 5). t t igher doses (0.25 mg/kg) p roduced a sedative ac t ion usually last ing for 45 rain. These results were observed be tween 2 groups of 3 animals each as well as within 2 animals in which b o t h cauda te and h y p o t h a l a m i c sites suppor ted ICSS. The order of site s t imula ted was coun te rba lanced .
ltis t o logy
The final e lec t rode loca t ions for all 12 animals for caudate and h y p o t h a l a m i c sites are presen ted in Fig. 6. Maximum pene t r a t i on for the caudate sites occurred at 14.5 t h rough 15.0 A.P. For the h y p o t h a l a m i c sites 10.5 th rough 12.0 A.P.
D I S C U S S I O N
The results of this s tudy d e m o n s t r a t e tha t the squirrel m o n k e y can be used to invest igate drug effects on brain self-s t imulat ion. Cons i s ten t and repl icable results were ob ta ined when e i ther the head of the caudate nucleus or the MFB wi th in the lateral h y p o t h a l a m u s was s t imula ted .
Since rates and th resho lds of ICSS elicited from the caudate nucleus or the h y p o t h a l a m u s are affected by a m p h e t a m i n e or CPZ admin i s t r a t ion , these drugs p robab ly act on DA as well as NE con ta in ing neurons . Low doses of a m p h e t a m i n e (0.5 mg/kg) faci l i tated low rates of ICSS
H G . 3. (A) Dose - r e sponse curve for c h l o r p r o m a z i n e e f f ec t s o n r a t e o f s e l f - s t i m u l a t i o n f r o m b e a d o f c a u d a t c (N = 6 ) or media l f o r e b r a i n b u n d l e (MFB) in the la tera l h y p o t h a l a m u s (N = 6 ) o f squi r re l m o n k e y s . Ver t i ca l b a r r e p r e s e n t s s t a n d a r d e r ro r o f the m e a n . (B) D u r a t i o n o f a c t i o n o f c h l o r p r o m a z i n e o n r a t e o f s e l f - s t i m u l a t i o n f r o m the head o f the c a u d a t e (N =
6) o r MFB (N = 6) b r a i n sites. Ver t i ca l b a r r e p r e s e n t s s t a n d a r d e r r o r o f the m e a n .
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FIG. 4. C u m u l a t i v e r e sponse r eco rd for o n e squi r re l m o n k e y t ha t rece ived dosages o f 0.5 (A), 1.0 (B), a n d 2 .0 (C) m g / k g o f c h l o r p r o m a z i n e . Brain s i tes s t i m u l a t e d were the h e a d o f the c a u d a t e a n d the med ia l f o r e b r a i n b u n d l e (MFB) in the la tera l h y p o t h a l a m u s .
154 SPENCER AND REVZIN
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1"1(;. 5. Cumulative response record for one squirrel monkey that received dosages of 0.05 or 0.10 mg/kg of chmidine. Brain site stimulated was either head of the caudatc or the medial forebrain bundle (MFB) in the lateral hypothalamus. Arrow indicates point when drug was given.
from b o t h sites. One dose of a m p h e t a n m l e (1.0 mg/kg) facil i tated ICSS from MFB while p roduc ing mixed effects
of fac i l i ta t ion and inh ib i t ion at cauda te sites. This result would suggest that the la tency of the inh ib i to ry effect of this par t icular dose of a m p h e t a m i n e on ICSS is shor t e r in the cauda te than the MFB (possibly by act ing on more or new aminergic pa thways) . A dose of 2.0 mg/kg b locked I( 'SS at b o t h sites. Doses of 0.5 and 1.0 mg/kg of CPZ produced larger effects on cauda te than MFB ICSS while at 2.0 mg/kg b o t h sites failed to suppor t ICSS. A l though this f inding might be part ial ly expl icable in terms of CPZ's known effects on dopam i ne - con t a i n i ng neu rons [1 ,16] the issue is p rohab ly more complex . For example in rats, CPZ adminis te red via imp lan ted cannu la d i rected into the caudate nucleus blocks I( 'SS elicited from the hypo- tha lamus [13 ] . The ac t ion is fairly select since app l ica t ion of CPZ to the cor tex did not affect rates of I( 'SS f rom the hypo tha l amus . The b lockade of I)A receptors in the cauda te appears to inhibi t I( 'SS in the hypo tha l amus . As would be expec ted , low doses of CPZ (0.5 mg/kg) also affect I( 'SS l rom caudate in the present exper imen t . At higher doses (i.e. 2.0 mg/kg) CPZ may have more general effects on ICSS at o t h e r brain sites via its more widespread inf luence on o the r amine systems.
t l igh doses of a m p h e t a m i n e 1,2.0- 10.0 mg/kg) or CPZ (2.0 mg/kg) had much longer du ra t ions of ac t ion on behavior elicited from the head of the caudate as compared with the hypo tha l amus . This result would suggest tha t high dosages of these drugs, using ICSS as a behavioral measure ,
tend to act on DA con ta in ing regions of the brain for longer periods than on noradrenerg ic sites. This i n t e rp re t a t i on is s t r eng thened by the f inding that cauda te se l f -s t imulat ion was inh ib i ted for 4 days fol lowing a 10 mg/kg dose of a m p h e t a m i n e while wi th in the same animal h y p o t h a l a m i c sel f -s t imulat ion was observed af te r 36 hr. The hypothes i s [261 that these drugs act pr imari ly wi th in the hypo- tha lamus is at best incomple te . If these drugs do act on a c o m m o n subs t ra te for 1CSS comparab le th resholds and dura t ions of drug ac t ion would be expec ted .
In cont ras t to the general ized effects of a m p h e t a m i n e or ( 'PZ t h r o u g h o u t tile ( 'NS, the hypo tens ive drug c lonid ine only appears to act on noradrenerg ic neurons [ 1 4 ] . Clonidine has known effects on b o t h cardiovascular and behavioral processes med ia ted by NE neurons in the hypo tha l amus . For example , when c lonid ine is placed direct ly in to the h y p o t h a l a m u s via cannula , a r educ t ion in heart rate and a lowering of b lood pressure occurs 141 and large a m o u n t s of eat ing behav io r are observed [5 ] . The hypothes i s tha t ICSS in the h y p o t h a l a m u s , which con ta ins NE neurons , should be affected to a greater degree than caudate I( 'SS received suppor t f rom the present findings, in animals with two func t iona l e lect rodes , ICSS from hypo- thalamic sites was b locked while ICSS t'rom the caudate was much less affected. The f inding tha t caudate ICSS is still ma in ta ined while h y p o t h a l a m i c I( 'SS is b locked by c lonidine would suggest tha t o the r t r ansmi t t e r s besides NE and o t h e r pa thways besides the MFB also play an impor t an t role in the suppor t of ICSS.
D R U G E F F E C T S ON S E L F - S T I M U L A T I O N B E H A V I O R 155
I
I LI
FIG. 6. Cross sections of squirrel monkey brain tissue taken through 4 an te r ior -pos te r ior (AP) levels. Each black dot represents final electrode penetration. All electrode implants were bilaterally represented. Abbreviations: Ca: Nucleus caudatus; SL: Area ~pta l i s pars lateralis; SM: Area septalis pars medialis, A: Nucleus accumbens septi; R: Gyrus rectus; ('1,: Claustrum; ('i: Cingulum; SS: Stratum subcallosum; CC: Corpus callosum; CI: Capsula interna; Olf: Area olfactoria; I-.': Fornix: RaO: Radiatio olfactoria profunda; CoA: Commissura anterior; TeM: Fasciculus telencephalicus medialis (median forebrain bundle); O1H: Fasciculus olfactorius hippocainpi (diagonal band of Broca); llCh: Chiasma nervorum opt icorum (optic chiasma); CE: Capsula externa; CEx: Capsula extrema: Un: l-.asciculus uncinatus;
I. Anlezark, G. M., G. W. Arbuthnot t , J. E. Christie and T . J . 7. (.;ergen, J. A. and P. D. Maclean. A stereotaxic atlas of the Crow. Role of cerebral dopamine in the action of psychoactive drugs. Br. J. Pharmac. 41 : 406 407, 1971.
2. Arbuthnot t , G. T.. K. Crow, K. t.'uxe, L. Olson and U. Ungerstedt. l)epletion of catecholaminc in vivo induced by electrical s t imulat ion of central monoaminc pathways. Brain Res. 24: 4 7 1 - 4 8 3 , 1970.
3. Axelrod, J. Noradrenaline: f a t e and control of its biosynthesis. Science 173 :598 606, 1971.
4. Boudier, tt. A. J. and J. M. van Rossum. Clonidine-induced cardiovascular effects after stereotaxic application in the hypotha lamus in rats..L Pharm. Pharmac. 2 4 : 4 1 0 - 411, 1972.
5. Broekkamp, C. and J. M. van Rossum. Clonidine-induced int rahypothalamic s t imulat ion o f eating in rats. Psycho- pharmacologia 2 5 : 1 6 2 168, 1972.
6. Domino, E. t.. Discussion of paper. In: P~ychotomirnetic drugs, edited by D. tt. I 'fron. New York: Raven Press, 1970, pp. 146 148.
squirrel monkey ' s brain ¢saimiri sciureus). U.S. Department of Health, Education, and Welfare, National Insti tutes of Health, Bethesda, Maryland. 1962.
8. German, D. and D. M. Bowden. Catecholamine systems as the neural substrate for intracranial serf-stimulation: A hypothesis. Brain Res. 73 :381 ..419, 1974.
9. Glowinski, J. and J. Axelrod. Effects of drugs on the uptake, release and metabolism of II3 norepinephrine in the rat brain. .L Pharmac. exp. Ther. 149: 43, 1966.
10. Haymaker, W., IS. Anderson and W. Nauta. 77re ltypothalamus. Springfield, Illinois: Charles C. Thomas. 1972.
11. t lernsworth, B. A. and M. J. Neal. The effect of st imulant drugs on the release of acetylcholine from the cerebral cortex. Br. J. Pharmac. 32: 416, 1968.
12. Justesen, D. R . , . I .C . Sharp and P. B. Porter. Self-stimulation of the caudate nucleus by instrumental ly naive cats. J. comp. physiol. P~vchol. 56 :371 374, 1963.
156 S P E N C E R A N D R E V Z I N
13. Keats, E. M. The effects of intracaudate injections of chlor- promazine on condit ioned avoidance and selt-stimulatit)n behavior. Unpublished Ph.D. dissertation. University of California, San Francisco. Dissertation Abstract 297 l-B, 34(6), 1973.
14. Laverty, R. and K. M. Taylor. Behavioral and biochemical effects of 2-(2,6-dichlorophenylamino)-2 imidazoline hydro- chloride (ST 155) on the central ncrvous system. Br. .L Pharmac. 35: 2 5 3 - 2 6 4 , 1969.
15. 1.indvall, O. and A. Bjorklund. The organization of the uscending catecbolamine neuron systems in the rat brain. Acta physiol, scand. Suppl. 4 1 2 : 1 48, 1974.
16. Moore, K. Biochemical ct~rrelates of the behavioral effects of drugs. In: /In httroduction to P~vchopharmacology, edited by R. Rech and K. Moore. New York: Raven Press, 1971, pp. 79-- 133.
17. Phillips, A. G. and 1t. C. l.ibiger. Dopaminergic and nor- adrencrgic substrates of positive reinforcement: differential effects of d -and I-amphetamine. Science 179: 5 7 5 - 5 7 6 , 1973.
18. Olds, J., K. G. Killam and Bach-y-Rita. Self-stimulation of the brain used as a screening method for tranquilizing drugs. Science 124:265 266, 1956.
19. Olds, M. 1-. and M. lto. Fffects of chlorpronaazinc, chlor- diazepoxide and pcntobarbital on neuronal excitability in thc medial lbrebrain bundle during self-stimulation behavior. Neuropharmacoh)g.v 1 2 : 1 1 1 7 - 1 1 3 3 , 1973.
20. Olds, M. E. and A. Yuwiler. Effect of brain st imulation in positive and negative reinforcing regions in the rat on content ~1" catecholamines in hypotha lamus and brain. Brain Res. 36: 3 8 5 - 3 9 8 , 1972.
21. Randrup, A. and 1. Munkvad. Correlation between specific effects of amphetamines on the brain and on behavior. In: Current Concepts on Amphetamine Abuse. edited by 1.i. Ellinwood and S. Cohen. Proceedings t~ta workshop, Duke University, Durham, N.('., Washington, I).C.: U.S. Governnaent Printing Office, 1970, pp. 17 -25.
22. Ritter, S. and L. Stein. Self-stimulation of the I~cus coeruleus. Fedn Proc. 31: 820, 1972.
23. Siegal, S. Nonparametric Statistics fi)r the Behavior Sciences. New York: McGraw-Hill, 1956.
24. Stein, 1,. Self-stimulation of the brain and the central s t imulant action of amphetamine. Fedn Proc. 23: 836, 1964.
25. Stein, 1.. Chemistry of reward and punishment . In: Psvcho- pharmacolog),. A Review o f Progress I c157 196 7, editcd by D. H. Efron. Washington, D.C.: U.S. Government Printing Office 1968, p. 105 123.
26. Stein, L. Facilitation of behavior by amphetamine. In: Psycho- mimetic Drugs, edited by D. H. Efron. New York: Raven Press, 1970. pp. 137- 145.
27. Stein, I.. and C. D. Wise. Release of norepinephrine from hypotha lamus and amygdala by rewarding medial forebrain bundle st imulation and amphetamine . J. comp. physiol. Psychol. 6 7 : 1 8 9 199, 1969.
28. Unemoto , M. and R. Kido. Depressing effect of methamphct - amine on self-stimulation in the cat. Nature 2 1 6 : 1 3 3 134, 1967.
29. Van Rossum, J. M. Mode of action of psycbonlolor stimulating drugs. Int. Rev. NeurohioL 12: 309--384, 1970.
30. Winer, B. J. Statistical pr#wiple.~ hi Experimental Design. New York: Mc(.;raw-Hill, 1973. p. 518.
