Camp. Biochem. Physiol. Vol. 8OC. No. 2, pp. 331-336, 1985 Printed in Great Britain 0306-4492185 53.00 + 0.00 c’ 1985 Pergamon Press Ltd PHARMACOLOGICAL CHARACTERISTICS OF THREE SILENT GIANT NEURONS, V-LPSN, v-1-VOrN AND V-VLN, IDENTIFIED ON THE VENTRAL SURFACE IN THE LEFT PARIETAL AND THE VISCERAL GANGLIA OF THE SUBOESOPHAGEAL GANGLIA OF AN AFRICAN GIANT SNAIL (ACHA TINA FULZCA FPRUSSAC) TOSHIO MATSUOKA, KAZUKO WATANABE and HIROSHI TAKEUCHI Department of Physiology, Gifu University School of Medicine, Gifu 500, Japan. Telephone: 0582-65- I241 (Rrceired 6 July 1984) Abstract-l. Three giant neurons, named V-LPSN, v-I-VOrN and V-VLN, were identified on the ventral surface of the left parietal ganglion and the visceral ganglion in the suboesophageal ganglia of an African giant snail (Achatina.fulica Ftrussac). They lacked the spontaneous spike discharges in the normal state. The pharmacological features of the three neurons, in relation to the principal common neurotransmitter substances and their derivatives were examined. 2. The V-LPSN (ventral-left parietal silent neuron) (diameter: about 130pm) is situated in the left parietal ganglion close to the visceral ganglion. The neuron was excited by histamine (the minimum effective concentration [MEC]: 3 x 10. 4 M) and inhibited slightly by acetylcholine (Ach) and its related substances. 3. The v-I-VOrN (ventral-left-visceral oral neuron) (diameter: about I30 pm) is situated in the left and oral part of the visceral ganglion. The neuron was inhibited markedly by dopamine (DA) (MEC: 3 x lO-4 M) and slightly by Ach and its related substances. No substance producing a marked excitation of the neuron has been found yet. 4. The V-VLN (ventral-visceral large neuron) (diameter: about 300 pm) is found in the centre of the visceral ganglion. The neuron was excited by L-norepinephrine (MEC: 10m4 M), DL-octopamine (MEC: 2 x 10e4 M), 5-hydroxytryptamine (MEC: 10. 4 M) and /3-hydroxy-L-glutamic acid (MEC: 10e4 M) and inhibited by DA (MEC:10--4M). GABA (MEC: 3 x 1O-5 M) and Ach (MEC: 10-4M). L-Epinephrine showed varied effects (MEC: IO-’ M), which were either excitatory or inhibitory. INTRODUCTION The numerous giant neurons, identified especially on the dorsal surface of the suboesophageal ganglia, of Achatina fulica FCrussac, have been used for physio- logical and pharmacological investigations in the neuronal level (Takeuchi et al., 1973, 1974, 1975, 1976, 1977; Takeuchi and Yamamoto. 1982; Ku and Takeuchi, 1983a,b). However, until the present time, only two giant neurons. V-RPLN (ventral-right parietal large neuron) and V-VNAN (ventral-visceral noisy autoactive neuron), have been identified on the ventral surface of the same ganglia. since the con- nective tissue covering this surface is very thick (Ku and Takeuchi, 1984). Following the last paper, three more giant neurons, V-LPSN, v-1-VOrN and V-VLN, which lack the spon- taneous spike discharges in the normal state, have been identified on the same surface. and the pharma- cological characteristics of the three neurons, in relation to the main common neurotransmitters and their derivatives, are examined in the present study. MATERIALS AND METHODS The African giant snails (Achatina filica Ferussac) were flown in from Okinawa (supplied by Koyo Yakuhin Co. Ltd.. President C. Fukuyama). The suboesophageal ganglia together with one or two peripheral nerves were dissected from the animal. Figure I is a schematic drawing of the ventral surface of the suboesophageal ganglia, where the three giant neurons examined in the present study are found. The localizations of the three giant neurons on the ventral surface of the suboesophageal ganglia are as follows: the V-LPSN (ventral-left parietal silent neurone) is not very large (diameter: about 130pm), and is situated in the left parietal ganglion close to the visceral ganglion on the extension line of the left anterior pallial nerve; the v-I-VOrN (ventral-left-visceral oral neuron), also not very large (diameter: about 130 {cm), is situated in the left and oral part of the visceral ganglion; the V-VLN (ventral-visceral large neuron) is a large neuron (diameter: about 300,um) found in the centre of the visceral ganglion near the root of the anal nerve. The three neurons lack the spontaneous spike discharges in the normal state. The electrophysiological arrangements for the present experiments were described in detail in previous commu- nications (Takeuchi ef al., 1974, 1975, 1976, 1977). The substances examined in the present study, which were obtained commercially, are listed in Table 1. These sub- stances were dissolved in the snail’s physiological solution (Takeuchi et al.. 1973) and administered directly to the dissected ganglia by means of bath application. The screen- ing tests of these substances were carried out at 5 x 10mm4 M, except for oL-octopamine, which was applied at IO-)M. The temperature of the experimental room was kept at 22 * 1’C. 331
Transcript
Camp. Biochem. Physiol. Vol. 8OC. No. 2, pp. 331-336, 1985 Printed in Great Britain
V-VLN, IDENTIFIED ON THE VENTRAL SURFACE IN THE LEFT PARIETAL AND THE VISCERAL
GANGLIA OF THE SUBOESOPHAGEAL GANGLIA OF AN AFRICAN GIANT SNAIL
(ACHA TINA FULZCA FPRUSSAC)
TOSHIO MATSUOKA, KAZUKO WATANABE and HIROSHI TAKEUCHI
Department of Physiology, Gifu University School of Medicine, Gifu 500, Japan. Telephone: 0582-65- I241
(Rrceired 6 July 1984)
Abstract-l. Three giant neurons, named V-LPSN, v-I-VOrN and V-VLN, were identified on the ventral surface of the left parietal ganglion and the visceral ganglion in the suboesophageal ganglia of an African giant snail (Achatina.fulica Ftrussac). They lacked the spontaneous spike discharges in the normal state. The pharmacological features of the three neurons, in relation to the principal common neurotransmitter substances and their derivatives were examined.
2. The V-LPSN (ventral-left parietal silent neuron) (diameter: about 130pm) is situated in the left parietal ganglion close to the visceral ganglion. The neuron was excited by histamine (the minimum effective concentration [MEC]: 3 x 10. 4 M) and inhibited slightly by acetylcholine (Ach) and its related substances.
3. The v-I-VOrN (ventral-left-visceral oral neuron) (diameter: about I30 pm) is situated in the left and oral part of the visceral ganglion. The neuron was inhibited markedly by dopamine (DA) (MEC:
3 x lO-4 M) and slightly by Ach and its related substances. No substance producing a marked excitation of the neuron has been found yet.
4. The V-VLN (ventral-visceral large neuron) (diameter: about 300 pm) is found in the centre of the visceral ganglion. The neuron was excited by L-norepinephrine (MEC: 10m4 M), DL-octopamine (MEC: 2 x 10e4 M), 5-hydroxytryptamine (MEC: 10. 4 M) and /3-hydroxy-L-glutamic acid (MEC: 10e4 M) and inhibited by DA (MEC:10--4M). GABA (MEC: 3 x 1O-5 M) and Ach (MEC: 10-4M). L-Epinephrine showed varied effects (MEC: IO-’ M), which were either excitatory or inhibitory.
INTRODUCTION
The numerous giant neurons, identified especially on
the dorsal surface of the suboesophageal ganglia, of
Achatina fulica FCrussac, have been used for physio- logical and pharmacological investigations in the neuronal level (Takeuchi et al., 1973, 1974, 1975, 1976, 1977; Takeuchi and Yamamoto. 1982; Ku and Takeuchi, 1983a,b). However, until the present time, only two giant neurons. V-RPLN (ventral-right parietal large neuron) and V-VNAN (ventral-visceral noisy autoactive neuron), have been identified on the ventral surface of the same ganglia. since the con- nective tissue covering this surface is very thick (Ku and Takeuchi, 1984).
Following the last paper, three more giant neurons, V-LPSN, v-1-VOrN and V-VLN, which lack the spon- taneous spike discharges in the normal state, have been identified on the same surface. and the pharma- cological characteristics of the three neurons, in relation to the main common neurotransmitters and their derivatives, are examined in the present study.
MATERIALS AND METHODS
The African giant snails (Achatina filica Ferussac) were flown in from Okinawa (supplied by Koyo Yakuhin Co.
Ltd.. President C. Fukuyama). The suboesophageal ganglia together with one or two peripheral nerves were dissected from the animal. Figure I is a schematic drawing of the ventral surface of the suboesophageal ganglia, where the three giant neurons examined in the present study are found.
The localizations of the three giant neurons on the ventral surface of the suboesophageal ganglia are as follows: the V-LPSN (ventral-left parietal silent neurone) is not very large (diameter: about 130pm), and is situated in the left parietal ganglion close to the visceral ganglion on the extension line of the left anterior pallial nerve; the v-I-VOrN (ventral-left-visceral oral neuron), also not very large (diameter: about 130 {cm), is situated in the left and oral part of the visceral ganglion; the V-VLN (ventral-visceral large neuron) is a large neuron (diameter: about 300,um) found in the centre of the visceral ganglion near the root of the anal nerve. The three neurons lack the spontaneous spike discharges in the normal state.
The electrophysiological arrangements for the present experiments were described in detail in previous commu- nications (Takeuchi ef al., 1974, 1975, 1976, 1977). The substances examined in the present study, which were obtained commercially, are listed in Table 1. These sub- stances were dissolved in the snail’s physiological solution (Takeuchi et al.. 1973) and administered directly to the dissected ganglia by means of bath application. The screen- ing tests of these substances were carried out at 5 x 10mm4 M, except for oL-octopamine, which was applied at IO-)M. The temperature of the experimental room was kept at 22 * 1’C.
331
332 TOsHl0 MAT~U~KA et al.
Suboesophageal ganglia
(Achatina fullca F6russac)
ventral surface
, 500Pm
Fig. 1. Schematic drawing of the ventral surface of the suboesophageal ganglia of Achatina fulica Ftrussac. In the left-parietal ganglion: V-LPSN, ventral left parietal silent neuron, In the visceral ganglion: v-I-VOrN, ventral-left- visceral oral neuron; V-VLN, ventral-visceral large neuron; V-VNAN, ventral-visceral noisy autoactive neuron; I-VMN, left-visceral multiple spike neuron; and r-VMN, right- visceral multiple spike neuron. In the right-parietal ganglia: V-RPLN, ventral-right parietal large neuron. a, Left anterior pallial nerve; b, left posterior pallial nerve; c, anal nerve; d, intestinal nerve; e, right posterior pallial nerve; and f, right
anterior pallial nerve.
RESULTS
The pharmacological characteristics of the three
giant neurons examined are summarized in Table 1.
On the V-LPSN (ventral-left parietal silent neuron)
Figure 2 shows the effects of substances examined on the V-LPSN membrane potential. Fewer sub- stances were effective on the neuron than on most giant neurons previously examined.
Only histamine (HA) produced a marked ex- citation of the neuron. The minimum effective con- centration (MEC) of the substance was about 3 x 10-4M. The two amino acids, erythro-p- hydroxy+glutamic acid (erythro-L-BHGA) and L-homocysteic acid (L-HCA), had slightly excitatory effects, but sometimes they had almost no effect.
The three cholines, acetylcholine (Ach), pro- pionylcholine (Pch) and butyrylcholine (Bch), produced to the same degree a slight and brief hyperpolarization of the neuron. DL-Octopamine (DL-OA) and S-hydroxytryptamine (5-HT) also had slight inhibitory effects, but sometimes the two substances were not effective. Dopamine (DA), L-norepinephrine (L-NE) and L-epinephrine (L-E)
showed almost no effect on the V-LPSN.
On the v-l-VOrN (ventral-left-visceral oral neuron)
Figures 3 and 4 represent the effects of substances on the v-1-VOrN membrane potential. Like the v- LPSN, the neuron was affected by fewer substances than most giant neurons.
Table 1. Pharmacological characteristics of the three giant neurons identified on the ventral surface of the suboesophageal ganglia of Achatina jiika FCrussac (bath application, screening at 5 x 10m4 M)
E, excitatory effects. SE, slightly excitatory effects. I, inhibitory effects. SI, slightly inhibitory .&Texts. Var, varied effects. (-), no effect. sy, synaptic influences. *, screening test at IO-‘M because DL-compound used. In parentheses, minimum effective concentration in M.
Pharmacology of Achatina neurons 333
V-LPSN 20mV
t i 04M DL-Octoptninr
B- _...~___.___..^__.___ ._..__.._.___._...--
t 5x I 04M 5-Hydroxytrypt~~ine
C
1 5X 1 o-% L-Homocyrtrie acid
D ./-- - ./----h
-ii t
SX I 04U erythro-pklydroxy-L-giutamic acid
E
t 5x I Om4hi Hittamins
F - _?.i---“--
t 5x I c4M Acstylcholins
Fig. 2. Effects of oL-octopamine at lo-‘M, and S-hydroxytryptamine, homocysteic acid, erythro-p- hydroxy-L-glutamic acid, histamine and acetylcholine at 5 x 10e4 M on the V-LPSN (ventral-left parietal silent neuron) membrane potential (bath application). Spike heights were cut electrically. Traces A and D were recorded from a V-LPSN; traces B, C, E and F were recorded respectively from four different V-LPSNs. Vertical bar, the calibration for the membrane potential (20mV). Horizontal bar, the time
course (30 set). Arrows indicate applications of the substance being examined.
The three substances, L-HCA, erythro-L-BHGA and HA, produced a slight excitation of the neuron. Although the synaptic influences were observed by their application, undoubtedly they are considered to have directly affected the neuron examined, since the depolarization caused by these substances was clear. In some cases, however, they failed to show any effect on the neuron.
DA produced the inhibition of the neuron; its MEC was about 3 x 10m4M. L-NE had slightly in- hibitory effects, whereas L-E and DL-OA had almost no effect. Ach, Pch and Bch equally produced a slight and brief inhibition. 5-HT and GABA also had slightly inhibitory effects, but sometimes they failed to show any effect.
On the u- VLN (ventral-u~sceru~ large neuron)
Figures 5 and 6 show the effects of substances on the V-VLN. More of the substances examined were effective on the neuron than in the cases of the V-LPSN and the v-1-VOrN.
The neuron was excited markedly by L-NE, DL-OA, 5-HT and erythro-L-BHGA; the MECs were 10m4 M for L-NE, 2 x 1Oe’4 M for DL-OA, low4 M for 5-HT and 10e4M for erythro+BHGA. Among them, the application of RL-OA sometimes produced synaptic influences on the neuron. L-HCA and HA caused a slight excitation. However, L-E had varied effects (MEC: 10-j M), which were in some cases excitatory and in other cases inhibitory.
GABA produced a marked and gradual inhibition of the V-VLN (MEC: 3 x 10e5 M); whereas the three cholines, Ach, Pch and Bch, produced to the same degree an abrupt and brief inhibition (MEC: 1O-4 M).
DISCUSSION
The three giant neurons, V-LPSN, v-I-VOrN and V-VLN, were identified on the ventral surface of the subeosophageal ganglia of Achatina fulica Fkrussac. Their pharmacological characteristics in relation to
v-I-V
OrN
2O
mV
A
30ar
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r
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Fig.
3.
Eff
ects
of
dopa
min
e,
L-n
orep
inep
hrin
e,
5-hy
drox
ytry
tam
ine,
G
AB
A
and
hom
ocys
teic
ac
id
at
5 x
10e4
M o
n th
e v-
I-V
OrN
(v
entr
al-l
eft-
visc
eral
or
al n
euro
n)
mem
bran
e po
tent
ial
(bat
h ap
plic
atio
n).
Spik
e he
ight
s w
ere
cut
elec
tron
ical
ly.
Tra
ces
A a
nd D
wer
e re
cord
ed
from
a
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rN;
trac
es
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C
and
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ere
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rded
re
spec
tivel
y fr
om t
hree
dif
fere
nt v
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s. V
ertic
al b
ar,
the
calib
ratio
n fo
r th
e m
embr
ane
pote
ntia
l (2
0 m
V).
Hor
izon
tal
bar,
the
tim
e co
urse
(3
0 se
t).
Arr
ows
indi
cate
app
licat
ions
of
the
sub
stan
ce
bein
g ex
amin
ed.
v-I-V
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A
5x1Q
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1 er
ythr
o-p-
Hydr
oxy-
L-gl
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t
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cr4
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Prop
tony
lcho
llnt
E
_. _
1 5x
I
04M
Bu
tyry
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lina
Fig.
4.
E
ffec
ts
of
eryt
hro-
b-hy
drox
y+gl
utam
ic
acid
, hi
stam
ine,
ac
etyl
- ch
olin
e,
prop
iony
lcho
line
and
buty
rylc
holin
e at
5 x
lo-
’ M
on
the
v-1.
.VO
rN
mem
bran
e po
tent
ial
(bat
h ap
plic
atio
n).
Spik
e he
ight
s w
ere
cut
elec
tron
ical
ly.
Tra
ces
A a
nd B
wer
e re
cord
ed
from
tw
o di
ffer
ent
v-I-
VO
rNs;
tra
ces
C,
D a
nd
E w
ere
reco
rded
fr
om
a v-
l-V
OrN
. V
ertic
al
bar,
th
e ca
libra
tion
for
the
mem
bran
e po
tent
ial
(20
mV
). H
oriz
onta
l ba
r, t
he t
ime
cour
se (
30 s
e@. A
rrow
s in
dica
te
appl
icat
ions
of
the
su
bsta
nce
bein
g ex
amin
ed.
V-V
LN
2o
mv
3OI.C
A
----
----
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o
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U L-
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o
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lno
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04U
S-tiy
drox
ytry
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F
.-
I 04
M
Buty
rylc
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e
Fig.
5.
Eff
ects
of
do
pam
ine,
tn
orep
inep
hrin
e,
t-ep
inep
hrin
e (t
wic
e)
at
10s4
M,
tm-o
ctop
amin
e at
2 x
10e
4M
and
5hyd
roxy
tryp
tam
ine
at
10e4
M
on
the
V-V
LN
(v
entr
al-v
isce
ral
larg
e ne
uron
) m
embr
ane
pote
ntia
l (b
ath
appl
icat
ion)
. Sp
ike
heig
hts
wer
e cu
t el
ectr
onic
ally
. T
race
s A
an
d B
wer
e re
cord
ed
from
a V
-VL
N;
trac
es C
, D
and
E
wer
e re
cord
ed
resp
ectiv
ely
from
th
ree
diff
eren
t v-
VL
Ns.
V
ertic
al
bar,
th
e ca
libra
tion
for
the
mem
bran
e po
tent
ial
(20
mV
). H
oriz
onta
l ba
r,
the
time
cour
se
(30
set)
. A
rrow
s in
dica
te
Fig.
6.
Eff
ects
of
GA
BA
at
3 x
10e
5 M
, an
d er
ythr
o$-h
ydro
xy+g
luta
mic
ac
id,
acet
ylch
olin
e,
prop
iony
lcho
line
and
buty
rylc
hohn
e at
10
m4 M
on
the
V-V
LN
m
embr
ane
pote
ntia
l (b
ath
appl
icat
ion)
. Sp
ike
heig
hts
wer
e cu
t el
ectr
onic
ally
. T
race
s A
and
B
, tr
ace
C,
and
trac
es
D a
nd
E w
ere
reco
rded
re
spec
tivel
y fr
om t
hree
dif
fere
nt
v-V
LN
s.
Ver
tical
bar
, th
e ca
libra
tion
for
the
mem
bran
e po
tent
ial
(20
mV
). H
oriz
onta
l ba
r, t
he t
ime
cour
se (
30 s
et).
Arr
ows
appi
icat
ions
of
the
sub
stan
ce
bein
g ex
amin
ed.
indi
cate
ap
plic
atio
ns
of t
he s
ubst
ance
be
ing
exam
ined
.
V-V
LN
20
mV
30oo
t A
I’-,
3 x
16%
G
ABA
I o-
%
oryt
ttro-
p-L-
glut
enic
ac
id
C
F
: 5x
I
04M
Hl
otrm
lno
D
I04M
Ac
otyl
chol
lno
I o-
4M
i ~r
Opl
onyl
chol
ino
336 TosHro MATSU~KA et al.
principal putative neurotransmitters, such as amines, amino acids and cholines, and their related sub- stances were tested.
HA is considered to be a putative excitatory trans- mitter of the V-LPSN; Ach to be a putative inhibitory transmitter of the same neuron. DA and Ach are supposed to be putative inhibitory transmitters of the v-I-VOrN. However, no substance can be postulated yet to be an excitatory transmitter.
Fewer substances examined in the present study were effective on two giant neurons, the V-LPSN and the v-I-VOrN, than in the case of most giant neurons examined previously (Takeuchi et al., 1973, 1975; Takeuchi and Yamamoto, 1982; Ku and Takeuchi, 1983a,b, 1984). It is supposed that some substances which are not examined in the present study, for example some peptides, will be neurotransmitters of the two neurons.
On the other hand, numerous substances were effective on the V-VLN. It is possible that L-NE, 5-HT
and erythro-t-BHGA are putative excitatory trans- mitters of the v-VLN, and that DA, GABA and Ach are putative inhibitory transmitters. The inhibition of ail of the three giant neurons examined, including the V-VLN, caused by Ach may be due to the increase of membrane permeability to chloride ions, since the inhibition was abrupt and brief (Watanabe and Takeuchi, 1977).
Kerkut et at. (1975) described very precisely the mapping of identifiable giant neurons in the sub- oesophageal ganglia of a European garden snail, Helix aspersa. However, since they described the giant neurons on the dorsal surface of the sub- oesophageal ganglia, no comparison of our results can be made with theirs. Johansen et al. (1982) described the mapping of the giant neurones identified in the same ganglia of a European edible snail, Helix pomatia. They aiso reported the giant neurons found in the dorsal surface of the ganglia. Therefore, our results cannot be compared with theirs either.
Besides the giant neurons of Achatina fulica re- ported in the present and last (Ku and Takeuchi, 1984) papers, more giant neurons can be identified on the ventral surface in the suboesophageal ganglia of the animal. A study of the pharmacological features of more giant neurons on the same surface will be a subject of our investigations to be reported in the near future.
Acknowledgement-akin work was supported partly by the Professor Kato Memorial Research Fund for Physiology and Medicine.
REFERENCES
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