The effects of pH on afferent synaptic transmission in Plotosus electroreceptors

S176 THE EFFECTS OF pH ON AFFERINT SYNAPTIC TRANSMISSION IN PLOTOSUS ILECTRORECEPTORS YOSHIKO SUGAWARA~ HIROKO SATO* and SHOSAKU OBARA, Sch.

Med.,

Itabashi-ku,

Spontaneous markedly

at

no c h a n g e i n other

decreased The h i g h e r

at

discharges pH v a l u e s

however,

receptors

decreased to

afferent

increased

In c o n t r a s t , Isolated

Kaga 2 - 1 1 - ] ,

ICa's. at

orthodromic

pH,

levels

pH,

of

PSPs t o

and PSPs were i n c r e a s e d , decreased Direct

of

as PSPs a t

the

of

pH on t h e

of

lower

pH,

nerve terminals

at

lower

slightly

at

which

confirmed

of

nerve

of

the

F data

pH v a l u e s ,

discharges

of

of

Univ.,

with

afferent

postsynaptic

responses the

suggested which

in

at

pH 6 . 2

which

with

was s i m i l a r

pK(PSP)

a t pH 6 . 6 .

changes. situ

Both

of

a sustained

may e x p l a i n

the

ICa

outputs,

were s i m i l a r l y

mass r e s p o n s e

trains

and on t h e o r t h o d r o m i c

pH v a l u e s .

Peak ICa was

The a f f e r e n t

previous

induced

are pH.

n e r v e were s i m i l a r l y

with

pH.

higher

lower

pK(ICa)

peaks,

2 pH u n i t s higher

at

Plotosus at

K-blockers.

and f o r

from the over

the orthodromic

A comparison

spontaneous

are decreased

pH may s u g g e s t

only

polarization

graded F increase. of

but

impulses,

postsynaptic

externally

b u t more s t e e p l y

Teikyo

and a r e d e c r e a s e d

the presence

activation

Physiol.,

electroreceptors

7.2,

o v e r 3 pH u n i t s

for

PSPs recorded

lower

Dept.

Japan

the tonic than

responses in

sigmoidally

voltage

sensitivity

F (frequency)

of

lower

were V - c l a m p e d

lower the

Tokyo 173,

impulses

data. with

depolarization reverse

effects

responses.

CIRCLING OR ROLLING BEHAVIOR FOLLOWING UNILATERAL ELECTROLYTIC LESIONS OF THE VESTIBULAR SYSTEM IN RATS SHIROU MATSUOKA , FUMIO SHIHA , MOTOHIRO KATO and KATSUTOSHI KITAMURA Departments of Neurosurgery and Neurophysiology, Neurological Institute, Faculty of Medicine, Kyushu University, Fukuoka Unilateral lesions were made in the vestibular system to clarify which structure was responsible for circling or rolling behavior. They included I) the lateral and superior vestibular nuclei (LVN & SVN), 2) the inferior and medial vestibular nuclei (IVN & MVN) and 3) the intramedullary part of the vestibular nerve. The circling or rolling behaviors were observed following systemic administration of dopamine agonists, apomorphine or methamphetamlne, and dopamine antagonist haloperidol. The levels of dopamlne (DA) and homovanillic acid (HVA) in the striatum of rats with circling behaviors were assayed by the gas chromatographic-mass spectrometric method. Rats with lesions in LVN & SVN did not show any circling or rolling behavior spontaneously, while they showed circling behavior toward the intact side in response to apomorphine. On the other hand, rats wlth unilateral lesions in IVN & MVN produced spontaneously transient rolling behavior toward the lesioned side and showed circling behavior toward the lesioned side in response to apomorphine. Methamphetamine did not enhance the circling behavior in rats with each lesion. Haloperidol completely blocked the circling behavior, suggesting that the circling behavior was DA-dependent and probably mediated by the ascending vestibulo-thalamo-striatal pathway. No differences between DA metabolism were found in the striatum on both sides. Unilateral lesions of the vestibular nerve caused tight long-lasting rolling behavior, but did not respond to DA agonists or DA antagonist, indicating that the rolling behavior was DA-independent.

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