CENTRAL DEPRESSANTS AND EVOKED CLICK RESPONSES WITH SPECIAL REFERENCE TO THE RETICULAR FORMATION IN THE CAT

CENTRAL

DEPRESSANTS

WITH

SPECIAL

AND

EVOKED

REFERENCE

TO

FORMATION

CLICK

THE

IN THE

RESPONSES

RETICULAR

CAT

SHUJI TAKAORI, YOSHIHISA NAKAI, MASASHI SASA AND KIRO SHIMAMOTO Department of Pharmacology, Facultyof Medicine, KyotoUniversity, Sakyo-ku, Kyoto Receivedfor publicationApril 7, 1966

The

present

rhythmic

have found

pentobarbital

magnitude

evoked click responses the

mechanisms

tatory

functions

by Moruzzi

chloralose

colliculus.

Urethane

only a progressive

stem RE

sodium, chloralose

of the auditory

investigators.

of the recruiting

In the previous

ascending

formation

the

inhibitory

Domino

responses.

(RF)

in the

and

facili

(5) and Killam (6)

response by barbiturates relay through

is due to

the ascending

papers (1, 3), small doses of pento

are likely

impulses to the auditory

in small

facilitating

ethyl alcohol are quite

(4), the ascending

and chlorpromazine

Furthermore,

without

and

ensuing

cat caused by

chlorpromazine

reticular

of the recovery cycle in the thalamic

influence of the brain

and

decrease in the cortical

role of the

and Magoun

that the potentiation

a release phenomenon

and

click responses

of central

potentials

conditions.

cortical

have been discussed by many

have emphasized

barbital

producing

demonstration

brain

the evoked

cortex of the unanesthetized

sodium,

of the

in the inferior

in their actions,

Since

that

affected by change of environmental

that

the

have reported

in the auditory

are easily

doses increase unique

(1-3)

after-discharges

click stimuli they

authors

cortex

to facilitate by inhibiting

the transmission the activity

of

RE The essential role of the RF in modification of the evoked auditory responses has been described by Hernandez-Peon et al. (7, 8), Desmedt et al. (9) and Chin et al. (10). However,

the complex

still remains

nature of interaction

responses and the RF

to be settled in detail.

In the present experiments responses

between the auditory

in the auditory

administration

of central

the effects of electrical

stimulation

of the RF on the click

cortex and the relay nuclei were studied depressants

before and after the

in the cat. METHODS

The encephale isole preparations fixation

of the animals,

to those reported at least earlier 高折

修 二 ・中井

operative

previously

of about procedures

75 adult cats of either sex were used. and delivery

(1-3). The recording

than 3 hours after the termination 義 尚 ・笹

征 史 ・島本

暉朗

of click stimuli

The

were similar

of the evoked potentials was not started of ether inhalation

in a sound-proof

room at the room temperature of 28±1`C. The potentials recorded by oscilloscope (San'ei Sokki, Type UB-203) were photographed using a long-recording camera. The EEG was monitored on ink-writing oscillograph (San'ei Sokki, Type IR-102). The RF was stimulated with square waves delivered from an electronic stimulator (Nihon Koden, Type MSE-3) through paired dental brooches, insulated except the tip with about 2 mm interval. An interval of each click was 5 seconds. RF stimulation (1.0 msec, 300/sec) for period of about 7 seconds was started 1 second before certain clicks. Accordingly, one set of two click responses was obtained during a period of RF stimula tion. The sites of stimulating electrodes in the RF (F: 4 to 12, L : 3, H : 1 to -10) were determined according to the topographical map of Snider and Niemer (11), and were confirmed histologically after the termination of the experiments by fixing the brain with intracarotid injection of formaldehyde. Pentobarbital sodium, chloralose, urethane, ethyl alcohol and chlorpromazine hydro chloride dissolved in Ringer or saline solution were infused into the ulnar vein at a speed of 100 ml/hr. RESULTS 1. Click responses during arousal and resting states The vian

auditory

gyrus

evoked

of the auditory

as the medial

geniculate

potentials cortex body

were

simultaneously

and one of the

of thalamus,

relay

inferior

, recorded from nuclei of auditory

colliculus

or cochlear

the left ectosyl pathway such nucleus.

FIG. 1. Evoked click responses during arousal and resting states. AC : Auditory cortex (middle ectosylvian gyrus, MG : Medial geniculate body of thalamus. IC : Inferior colliculus, CN : Cochlear nucleus.

As

shown

in Fig. 1, the

body

decreased

manifested cortical and

an EEG

evoked click

usually

in amplitude,

arousal

pattern.

intermingled

medial

geniculate

the

click responses

hand,

in connection

responses

with

when

During

with body

in the auditory

in the

bursts, rather

inferior

the pattern

cortical

EEG

responses

increase and EEG

and

in

sites of stimulation

before, during

cochlear (Fig.

tion of certain amplitude.

areas of the RF increased

Fig.

3 shows

stimulation

on the EEG

motor

auditory

and

decreased

cortex of

in the auditory

nucleus

On

In

cortex, cortex

other

were not modified

was changed

a series

of the

according responses

of the cases, the click responses in

by RF stimulation.

significantly

However,

the cortical

stimula

click responses

the

accord

the spike poten evoked by click

in amplitude

and

after-discharges

disap

peared during and after RF stimulation. In some cases, however, the click spike poten tials

and the

facilitated EEG

ensuing

in the

motor

desynchronized increasing resulted click

responses

and

8/sec

click

produced

responses

reported

in

stimulation responses stimulation repetitive

turned In

the

to the

these

cases,

of RF stimulation of amplitude

of the

a disappearance

of the

after-discharges.

Repeated

titive

cortex

the intensity

were

although

pattern.

in a reduction

rhythmic

of

after-discharges

by RF stimulation,

the

stimuli a

previous

4).

was about click

stimuli

to the

onset

of

the

auditory

also modified (Fig.

at a frequency

series

in the

repe

cortex,

paper

(2).

the repetitive

The

duration

10 seconds

as RF click

of RF and

the

started

at 2 seconds

of

stimulation.

Fic;.

delayed Then,

both click

RF

and reticular

stimuli

were

the

cortex

the

of the EEG arousal

usually

rhythmic

motor pattern

of RF from

corticies.

pattern in the motor tials in the auditory

ensuing

influence recorded

the manifestation

stimuli

In many

cortex were reduced in amplitude

geniculate

1).

Fig. 2 illustrates

and after RF stimulation.

the auditory

with

in the RF.

in the

magnitude.

2. Influence of RF stimulation on click responses in the auditory cortex An amplitude of the click responses in the auditory cortex to the

medial

of a synchronized

the click an

colliculus

of the

spontaneous

exhibition

spindle

showed

the

cortex

2.

Influence

click RF-s

of

response : Reticular

RF in

stimulation

the

auditory

formation

on

single

cortex. stimulation.

in

FIG.

3.

Influence of RF stimulation on MC : Motor cortex, AC : Auditory

EEG recorded cortex ; Time

from the motor and scale : 1 second.

auditory

cortices.

FIG. 4. Influence of RF stimulation on repetitive click responses (8/sec) in the auditory cortex. MC : Motor cortex. AC : Auditory cortex, RF-s : Reticular formation stimulation.

FiG.

5.

Inhibition with

the

and sites

FIG. 6.

interrupted in

amplitude.

stimulation

of

Therefore, single

click

animals. plane,

the stimuli

Fig. and

of

influences

RF

cortical

click

responses

varied

of

placement

stimulation the

in

the

RE

decreased

responses

was

also

the

repetitive

observed

in

click

res

response

to

evoked

by

sites

in about

20

from

the

median

circle)

or faci

RF.

of RF

assessed

5 is a sagittal

shows

the

the

electrode

facilitation

areas

were

of

stimulation.

Mostly, The

certain

RF

Stimulating

simultaneously.

ponses

facilitation of

stimulation in correlation

section

the sites of stimulation

of the

on

the

to the

brainstem

producing

cortical

responses

stimulating 3 mm

the inhibitory

apart

(filled

litatory (open circle) effect. In general , the inhibitory sites were diffusely distributed in the RF. On the other hand, the facilitatory sites were localized mainly in the pontine RF and rarely in the rostral and caudal parts of RE Fig . 6 demonstrates the histolo gical placement of stimulating electrode in the RE 3. Influenceof RF stimulationon click responsesin the auditory relay nuclei Fig. 7 illustrates the effects of stimulation of the inhibitory area of RF (F: 2, L : 3, H : -1) on the click responses in the auditory cortex and the relay nuclei of the auditory pathway. During RF stimulation the amplitude of the click responses recorded from the auditory cortex and medial geniculate body was decreased by 30.1 and 25.6%, respec tively (Table 1). On the other hand, the magnitude of the click responses in the inferior colliculus was not changed by RF stimulation. The click responses in the cochlear nucleus showed a slight decrease in amplitude (15.3%) during RF stimulation.

FIG. 7. Influence of RF stimulation on single click responses in the auditory cortex (AC) , medial geniculate body (MG), inferior colliculus (IC) and cochlear nucleus (CN) . TABLE 1. Inhibition inferior

* : Per

cent

of click

colliculus

change

of

responses

and cochlear

the

click

in the auditory nucleus

responses

caused

in each

cortex , medial by RF stimulation

animal

is mean

geniculate body, (RF : 2 , 3, 1).

value

of

10 tri

als.

4. Effectsof central depressantson the modifiedclick responsesin the auditorycortexby RF stimula tion It was reported previously (1) that pentobarbital sodium, chloralose and chlorpro mazine in the small doses increased the amplitude of the click responses in the auditory cortex and that these depressants in the large doses depressed the responses. These results

FIG.

8.

Effect

responses

FIG.

9.

Effect

of

of

pentobarbital

caused

chloralose

by

on

RF

the

sodium

on

the

inhibition

cortical

click

of

cortical

click

stimulation.

inhibition

of

responses

caused

by

RF

stimulation.

were

also

confirmed

in the present

kg of pentobarbital on the cortical

sodium

abolished

click responses,

promazine behaved of 30 mg/kg (Figs. 11) abolished

experiments.

The

apparently

as shown

the inhibitory

in Fig. 8.

similarly with pentobarbital 9 and 10) and chlorpromazine

completely

the

depressing

effect

intravenous

In this

sodium. in the of RF

infusion effect

respect,

of RF

chloralose

above

stimulation and

Chloralose in the infused infused dose of 2 mg/kg

stimulation

on

the

4 mg/

cortical

chlor dose (Fig. click

responses. On barbital

the other

hand,

sodium,

FIG.

10. RF

Effect

of

11.

point

Effect

caused

by

in in

and

and

chloralose

stimulation Each

FIG.

urethane

chloralose

the

ethyl

alcohol

behaved

chlorpromazine.

on

three

the

inhibition

The

of

cortical

quite

present

click

differently

responses

caused

preparations.

figure

of

chlorpromazine

RF

stimulation.

represents

on

mean

the

of

inhibition

10 recordings.

of

cortical

from pento

experiments

click

responses

confirmed

by

the previous

findings

a progressive inhibition

of the click

the intravenous

Fic.

12.

(1) that

decrease

Effect

infusion

of

FIG.

infusion

of urethane

and

of the cortical

responses

by RF stimulation

caused

of 400 to 1,000 mg/kg

urethane

13.

the

in the amplitude

on

Effect

responses

the

of

inhibition

ethyl

caused

by

of

of urethane

cortical

alcohol

on

RF

stimulation.

the

click

inhibition

ethyl

alcohol

produced

only

Furthermore,

the

was invariably

observed

even

(Fig. 12).

effect

click responses.

responses

of

caused

cortical

The

by

click

RF

of ethyl

stimulatior.

alcohol on the inhibition ed a close resemblance

of the cortical click responses caused by RF stimulation to that of urethane,

parently depressed by RF stimulation ethyl alcohol (Fig. 13).

and the amplitude

show

of the responses was ap

even after the infusion of 400 to 800 mg/kg of

DISCUSSION The click responses of thalamus one.

recorded from

were smaller

However,

in amplitude

no significant

tude of the click responses ly implanted

electrode,

the alert alert

recorded

one, and

the arousal

from the inferior

the present authors

(13).

reported

and Rhines (14, 15) demonstrated

litatory influences. and Mancia

A dual ascending

click responses

that the

by Chin et al. (10)

resting

state in the acute

with the drowsy state, but not with the deep sleep

state in the unrestrained animals. The reticular formation is known to be not a homogenous Magoun

nucleus.

cat with chronical

in the deep sleep state than in the

the findings

it is considered

corresponds

in ampli

the resting and drowsy states than during

well with

Therefore,

unrestrained

body

the resting

colliculus and cochlear

(12) showed that the cortical

that the responses were smaller

encephale isole preparations

state than during

both states was observed

using the unanesthetized,

These results coincided

Huttenlocher

cortex and medial geniculate

between

in size and more stabilized during

one.

and

during

difference

In another series of experiments were larger

the auditory

the reticular

mechanism

structure

descending

in its function.

inhibitory

of the RF was demonstrated

(16) and Magnes et al. (17), who pointed

and faci by Cordeau

out the EEG synchronization

pro

duced by low-frequency stimulation of the brain stem RF. The present experiments also revealed the existence of both ascending inhibitory and facilitatory mechanisms of the RF in the auditory which

cortical responses.

was diffusely

cortical

distributed

High-frequency

in the RF resulted

stimulation

of the inhibitory

in a decrease

in amplitude

area of the

responses to single and repetitive click stimuli as well as in a desynchronization

of the EEG in the motor cortex. RF facilitated

the cortical

desynchronization the increase stimulation

of the facilitatory

it resulted in the similar

the stimulation

click responses.

click responses

intensity

The contrary

findings

and the EEG desynchronization

area in the RF suggested that the distribution

activating

system in the RF might be somewhat

inhibitory

system to the auditory and

although

EEG, and increasing

of the cortical

in the cortical

Demetrescu

of the certain areas of the pontine

click responses in amplitude,

of the cortical

the decrease in amplitude

However, stimulation

Demetrescu

different

caused between

caused by of the EEG

from that of the ascending

cortex. (18) reported

that

high-frequency

pontine RF produced variable effects on the thalamocortical visual cortex of encephale isole cats with lesions in the central

stimulation

of the

evoked potentials in the gray; i.e. stimulation of

the ventral RF inhibited the evoked potentials, while that of the dorsal RF facilitated them. Dumont and Dell (19) showed an increase in amplitude and a shortening of latency of the cortical

visual evoked

potentials

during

RF stimulation.

The excitation

and inhibition

of cortical

were described

by Fuster (20). The present

tion or inhibition

neuronal

of the cortical

firing in response to light by mild RF stimulation experiments

demonstrated

click responses varied according

that the facilita

to the sites of stimula

tion in the RE In the present recorded

experiments,

from the cochlear

RF stimulation

inhibited

nucleus and medial geniculate

slightly

the click responses

body, while the responses in

the inferior colliculus were not modified by RF stimulation.

The existence of the efferent

pathway from the insulo-temporal cortex to the cochlear nucleus was indicated by Desmedt et al. (9). If this indication is allowed, the slight inhibition of the click responses in the cochlear nucleus is assumed The previous chloralose thalamic

and

to pass through

observation

chlorpromazine

facilitated

the auditory

level of the cat, and that urethane

click potentials

in the auditory

also demonstrated the cortical

this efferent

pathway.

(1, 3) showed that the small doses of pentobarbital

of the ascending

colliculus. inhibitory

but not by urethane

firm the assumption of pentobarbital the reticular

and

that the facilitation

sodium, chloralose

inhibitory

mechanism,

ethyl alcohol.

The present sodium,

experiments

chloralose

These evidences

of the auditory

transmission

and chlorpromazine

both the evoked

effect of RF stimulation

click responses by the small doses of pentobarbital

chlorpromazine

only in the supra

and ethyl alcohol inhibited

cortex and inferior

the abolition

transmission

sodium,

on and

serve to con

by the small doses

resultes from the suppression

of

i.e. the release phenomenon. SUMMARY

The

modification

of the click responses recorded

from the auditory

cortex,

medial

geniculate body, inferior colliculus and cochlear nucleus induced by stimulation of the various sites of the reticular formation (RF) were studied in the encephale isoli prepara tions of cats. urethane

Moreover,

the effects of pentobarbital

sodium, chloralose,

and ethyl alcohol on the changes of the cortical

click responses caused by RF

stimulation were investigated. The results obtained were summarized 1. The click responses in the auditory cortex and medial geniculate in the resting state than in the arousal one, while the click responses liculus and cochlear nucleus did not change during 2. The

amplitude

of the cortical

decreased by high-frequency

responses

stimulation

chlorpromazine, as follows: body were larger

in the inferior col

both states. to single and

of the reticular

repetitive

inhibitory

click stimuli

area which was dif

fusely distributed in the RF. On the other hand, high-frequency stimulation of the reticular facilitatory area which was mainly localized to the pontine RF produced an increase in amplitude 3.

of the cortical

A slight decrease

in the medial geniculate 4.

was observed

body and cochlear nucleus, but the click responses in the inferior

colliculus was not influenced

by RF stimulation.

Small doses of pentobarbital

the depression

click responses.

in the click responses caused by RF stimulation

sodium,

chloralose

and

chlorpromazine

of the cortical click responses induced by stimulation

of reticular

abolished inhibi

tory effect

area. on the

However, cortical

urethane click

and

ethyl

alcohol

did

not affect

the reticular

inhibitory

responses. REFERENCES

1) NAKAI, Y. : THIS JOURNAL 14, 235 (1964) 2) NAKAI, Y. AND TAKAORI, S. : Ibid. 15, 165 (1965) 3) NAKAI, Y., TAKAORI,S. AND SHIMAMOTO,K. : Ibid. 15, 201 (1965) 4) MORUZZI, G. AND MAGOUN, H.W.: EEG clin. Neurophysiol.1, 455 (1949) 5) DOMINO,E.F.: J. Pharmacol. 115, 449 (1955) 6) KILLAM, E.K.: Pharmacol. Rev. 14, 175 (1962) 7) HERNANDEZ-PEON,R., SCHERRER,H. AND JOUVET, R.M. : Science 123, 331 (1956) 8) HERNANDEZ-PEON,R., JOUVET, R.M. AND SCHERRER,H.: Acta Neur. lat. amer. 3, 144 (1957), Cited from 9). 9) DESMEDT,J.E.: Neural Mechanism of the Auditory and Vestibular System, edited by RASMUSSEN,G.L., Thomas Publisher, Springfield

(1960)

10) CHIN, J.H., KILLAM, E.K. AND KILLAM, K.F. : EEG clin. Neurophysiol. 18, 567 (1965) 11) SNIDER, R.S. AND NIEMER, W.T. : A Stereotaxic Atlas of the Cat Brain, The University Press, Chicago (1961) 12) NAKAI, Y., SASA. M. AND TAKAORI,S. : THIS JOURNAL (in press) 13) HUTTENLOCHER,P.R. : EEG clin. Neurophysiol. 12, 819 (1960) 14) MAGOUN, H.W. AND RHINES, R.: J. Neurophysiol.9, 165 (1946) 15) RHINES, R. AND MAGOUN,H.W.: Ibid. 9, 219 (1946) 16) CORDEAU,J.P. AND MANCIA. M.: EEG clin. Neurophysiol. 11, 551 (1959) 17) MAGNES,J., MoRuzzl, G. AND POMPEIANO, O.: Fed. Proc. 20, 336 (1961) 18) DEMETRESCU,M. AND DEMETRESCU,M. : EEG clin. Neurophysiol. 14, 602 (1962) 19) DUMONT, S. AND DELL, B.: Ibid. 12, 769 (1960) 20) FUSTER, J.M. : Science 133, 2011 (1961)

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