網膜神経節細胞群の周期的同期発火による視覚誘発性逃避行動の誘発(第23回大会 優秀発表賞抄録)

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

The

.lapanese

fournatofRsychonomicScience

2005,Vol.24,No.1,107 108

Summary

ofAwarded

PresentationIPOI

Triggering

of

escape

discharges

ofbehavior

by

oscillatory

synchronized

retinal

_ganglion

cells

in

frogs

Shoko

HoNDA,

Mie

GANGi,

Yasuhiro

HoRiucHi,

Hjroshi

IsHIKANE,

and

Masao

TAcHIBANA

11he

University

of

Tokyo'

In

the retinas of frogs synchronized discharges accompanied

by

_r-range oscillations

(the

oscillatory synchronization,

OS}

are generated among OFF-sustained

_ganglion

cells

(dimming

detectors)

in

response

to

a

dirnming

stimuLus.

We

have

already shown that an expanding dark spot

generates the retinai

OS

and elicits escape behavior, which isabolished whcn the

OS

is

suppressed

by aGABAA receptor antagonist. Rcccntly we observed that a

GABAc

receptor antagonist,

(1,2,5,6-tetrahydropyridine-4-yl) methylphosphinic acid

_(TPMPA),

enhanced the oscil]atory activit,y of

dimming

detectors.

In

the present study, we

investigatcd

how OS and escape behavior were

modulated when TPMPA was applied tothe retina. An

intraoeular

injection

of

TPMPA

potenti-ated escape behavior. Moreover, multi-electrode recordings from

isolated

retinas revealed thatthe

OS

was significantly enhanced by

TPMPA.

On

theother hand, TPMPA didnot affect theresponse

prepertiesof other gangLion cellswhich were not

dirnming

detectors.Furthermere, modulation of

the retinal

OS

by

_the

GABA

receptor antagonists was closely related tothe changes

in

escape

behavior. Consequently, we conclude that theOS may encode escape-related

information.

Key words: oscMatory synchrenization, escape behavior,retinal _gangljon cells

The

synchronized activities accompanied by r-range

(approximately

20 to

80

Hz)

oscillations

(the

oscillatory synchronization, OS) inthe CNS are as-sumed to

be

related tesensory and cognitive

process-ing

(Engel

et al. 2001). However, inthc visual

$ys-tems the functienal role of the

OS

has

yet to

be

elucidated.

We

have

shown that a

GABAA

receptor antagonist, bi¢uculline, suppresses the OS among

OFF-sustaincd

_ganglion ce)ls

(dimming

detectors)

in

frogs'retinas

(I$hikane

et al,,

1999).

In addition, an

intraocurar

injeetion

of

bicuculiine

abc)lishes the

e$-cape

behavior

of

frogs

to an expanding dark spot

which mimics an approaching _predator

(Gangi

et al.

2004).Recently,we have found thata

GABAc

recep-tor

antagonist enhances

the

oscillatory activity of

dimming

detectors

induccd

by a djmming stimulus

(Arai

et aL, 2004). Inthe _present study,

to

elucidate

the functionairole of _the

OS,

we

investigated

how

the GABAc re¢eptor antagonist affected the retinal

ganglion cellsand escape

behavior

offrogs.

* _{Departmentof Psychology,}

_Graduate

_School

of

Humanities and Sociology,The

University

of

To-kyo, 7L3-1

Hongo,

Bunkyo-ku,

Tokyo 113-O033

Methods

We used bullfrogs

(Rana

catesbeiana}

in

behavioral

and electrophysiological experiments which were

performed

in

accordance with the guidclines for the

care and use of animals

(The

University

of

Tokyo

and The Physiological

Society

of

Japan}.

Arlof the

experiments were performed ina dark room,

Behavioral

Experiments

We examined whether frogs exhibited an e$cape

behavior in response _to an expanding

dark

spot

(from

O

degree

toa variety of

final

sizes) _presented on

an

LCD.

The

finalsize was randomly varied

(1O

to

55

degrees indiameter;6_grades) whereas theexpansion

speed was fixedat 43 degrees _per second. Each frog

was testcd

before,

2

hours

after,and 1day after, an

intraocular

injcction

of a cc)mpetitive

GABAc

re-ceptor antagonist

((1,2,5,6-tetrahydropyridine-4-yl)

methylphosphinic acid,

TPMPA>.

Thc

TPMPA

{500

"M) was injected into both eyes under anesthesia,

and allof the frogs recovered completely within 2

hours.

The intraocularconcentration of the

TPMPA

was estirnated tobe apprQximate]y

50"M.

The es-Cepyright2005.The JapanesePsychonornic Society.Allrights reserved.

The Japanese Psychonomic Society

NII-Electronic Library Service

The JapanesePsychonomic Society

108 The

Japanese

Journal

of Psvchonornic Science Vol,24,No. 1

cape rate of the frogs was

defined

as the ratio

of the escape-observed trialstothe totalnumber of trials.

ElectrophysiologicalExperiments

Spike

discharges

of ganglion cells were recorded

with a _planar multi-electrode array from isQlated

retinas

(Ishikane

et al. 1999). The retinas were

sti-mulated with cxpanding

dark

spots, the

_parameters

of which were

identical

tothoseused forbchavioral

tests.

Aftcr

spike sorting, _{peri-stimu]us}time

histo-grams

(PSTHs),

auto-correlograms, and the power

spectra were calculated toevaluate the effects of the

TPMPA.

Results

Behayioral

Experiments

The

escape rate of the frogsincreased as

the

final

size of the cxpanding dark spot was enlarged.

An

intraocular injectienQf

TPMPA

also significantly

potentiatcd the escape

behavior

(N=5

frogs}.Two

hours after thc injection.the initialrelationshlp

be-tween

thefinalsize of

the

spot and the

frog

escape

rate was shifted tothe lefton the abscissa. The effects of theTPMPA wcre not apparent

1

day

after

the injection.

ElectrophysiologicalExperiments

Dimming

detectors

were observed to _generate

r-range oscillatory synchron[zed activity inresponse to the expanding dark spot. In addition, the

OS

and

the

discharge

rate werc significantly enhanced by

bath-applied TPMPA

_OOgeM),

Hewever, the peak

frequency

of

the

OS

in

the_power spectrum was not

obvious]y changed.

0n

_the other hand, _gang]ion

cells which were not

dimming

detectors_generated

transientresponses without detectableosci]lations to

the expanding dark spot. The

TPMPA

did not

in-duce

obvious changes

in

the profiles of the PSTHs and auto-correlograms, or significantly change the

discharge rates, Thus, TPMPA-induced _potentiation

of the escape

behavior

may

be

ascribed tothe

en-hanced OS of the

dimming

detectors.

Discussion

The present study

demonstrated

thatTPMPA, a

GABAc

receptor antagonist, enhanced OS of

dim-ming

detectors

and _potentiated escape

behavior.

In

addition, GABAc receptor-mediated mechanisms

may modulate

the

stimulus size

dependencc

of

es-cape behavior. We have already reported that

sup-pression of the OS by a

GABAA

receptor antagonist

abolished escape

behavior

<Gangi

et a!. 2004), and that

boLh

GABA

receptor antagonists increased the

discharge

rate of dimming detectors

{lshikane

et al,,

1999;Arai et al. 2004).Inadditien, theprescntstudy shows that the responses totheexpanding dark $pot

by

ganglion ce]ls which were not dimming

detectors

were not changed by TPMPA. Thus, only theretinal

OS of

dimming

detectors

correlated to the escape

behavior.

It

is

proposed that the retinal OS of

dim-ming detectors may encode essentia] escape-related

information.

References

AraL I.Yamada, Y. Asaka, T. & Tachibana,

M.

2004.

Light-evoked oscillatc)ry

discharges

in

retinal

glion cells are generated

by

rhythmic synaptic

inputs.

fournal

of

IVeurQphysiolog:yu

92,715-725,

EngeL

A.

K.

&

Singer,

W, 2001. Temporal binding

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Ishikane,

H. &

Tachibana,

M

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7he

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