Suppression of synaptic exocytosis through 5-HT1A receptor in cultured rat hippocampal neuron

SIOO

118

THE MECHANISMS HIPPOCAMPAL

MAKOTO

OSANAI,

KIM10 AKAGAWA,

Dept. of Physiology,

Long-term

Kyorin University

potentiation

presynaptic

KAZUHIKO

is attributable

([Ca2+le)

from the granule cells of the dentate gyrus to the CA3 pyramidal

the modulatory

of EPSC amplitude

activator of adenylyl cyclase, was applied, EPSC amplitude

119

of exocytotic

‘Dept. of Physiology,

Activation

EXOCYTOSIS

and paired-pulse

THROUGH

and formed autaptic connections. containing

was adjusted to around 50 r&l. When intrapipette

solution contained GTP-y-S (0.1mM). Application that synaptic exocytosis

was suppressed.

D,-LIKE

EIKO KOGA, TOSHIHIKO

dopaminergic

I-OH-DPAT

the EPSC irreversibly when pipette EPSC,

at presynaptic

terminal. Reduction

of hippocampal

neurons in culture.

1NHIBITlON

NEURONS

of CAMP mediated by

OF

GLUTAMATERGIC

1N THE RAT VENTRAL

SYNAPTlC

TEGMENTAL

AREA

MOMIYAMA Sakamoto, Nagasaki 852-8523

study was carried out using thin (200 urn) slice preparation (DA) on the non-NMDA

glutamatergic

excitatory

of 8-16 day old rat brain to elucidate

postsynaptic

currents

(EPSCs)

in the putative

(0.5 uM) at -60 mV, and were blocked by CNQX (5 uM). Bath application

t 10

of DA (30 PM) reduced the

of the evoked EPSCs by 37.2 + 2.69 % (mean + S E.M., n=9) of the control without affecting the holding current

Quinpirole

(30 PM), a D,-like receptor agonist, also reduced the EPSC amplitude

DA-induced sulpiride

were analyzed

neurons in the ventral tegmental area (VTA). EPSCs were evoked at 0.2 Hz in the presence of bicuculline

PM) and strychnine amplitude

suppressed

a

neurons

(3OpM). Intracellular free Ca2*

did not affect the quanta1 size of the asynchronous

RECEPTOR-MEDIATED

ONTO DOPAMINERGIC

Nagasaki Univ. School of Medicine,

patch-clamp

neurons. Hippocampal

Since 5-HT (10 @I) had almost same effect with that of 8-OH-DPAT,

5-HTIA receptor may underly decrease in the synaptic exocytosis

TRANSMISSION

18 l-8611

solution contained 0.3 mM GTP, bath-applied

of 8-OH-DPAT

5-HTIA receptor would be a major subtype of 5-HT receptors

A whole-cell

IN CULTURED

on synaptic transmission

APV (3OpM) and picrotoxin

(10 @I) reduced amplitude of autaptic EPSC reversibly, while S-OH-DPAT

the effect of dopamine

of

We examined effects of I-OH-DPAT,

in the cultured hippocampal

Effects of 8-OH-DPAT

concentration

Dept. of Physiology,

dependence

was not due to the change of

S-HT,* RECEPTOR

of cAMP through G-protein.

on the synaptic transmission

recording methods in a bath-solution

DOPAMINE

(PPM) on extracellular

but the [Ca2+],

and PPM decreased,

of synaptic transmission

Kyorin Univ. School of Medicine, Mitaka,Tokyo

by whole-cell

120

modulation

NEURON.

of S-HTiA receptor causes down-regulation

selective agonist of 5-HTi* receptor,

suggesting

of the

at the mossy fiber

MIKI KOGURE2, OSAMU TAJIMA2

2Dept. of Neuropsychiatory,

grew on glial micro-islands

increased

that the enhancement

OF SYNAPTIC

RAT HIPPOCAMPAL YAMAGUCHI’,

mechanisms

of the exocytosis

machinery.

SUPPRESSION

KAZUHIKO

release. But the modulatory mechanisms

using the autapse of the cultured neuron from rat dentate gyms region. When forskolin,an

EPSC did not change. This result suggested Ca2+-sensitivity

OF SINGLE

Mitaka, Tokyo 18 l-861 1

to increase in the transmitter

were not clear. For elucidating

AT MICROCULTURE

GYRUS REGION.

YAMAGUCHI

School of Medicine,

terminal, we analyzed the dependence

Ca2+ concentration

POTENTIATION

(LTP) in the mossy fiber pathway,

cells of the hippocampus synaptic exocytosis

OF SYNAPTIC

NEURON FROM RAT DENTATE

inhibition

(5 PM),

transmission

a D,-like

receptor

antagonist.

onto VTA DA neurons via DJike

by 48.7 + 11 I % (n=4) of the control.

from 33.5 + 3.49 to 2.57 + I .28 Oh(n-3) by simultaneous

of EPSC was antagonized

These

receptors.

results

suggest

that

DA inhibits

non-NMDA

application

of

glutamatergic