EFFECTS OF CENTRAL DEPRESSANTS AND STIMULANTS ON EEG ALTERATIONS INDUCED BY CAROTID COOLING AND WARMING

EFFECTS

OF

CENTRAL

ON

EEG

DEPRESSANTS

ALTERATIONS

CAROTID

AND

STIMULANTS

INDUCED

COOLING

AND

BY

WARMING

SHUJI TAKAORI AND KENZABURO TANABE Department of Pharmacology, Facultyof Medicine, KyotoUniversity, Sakyo-ku, Kyoto Receivedfor publicationSeptember21, 1964

The

influence

of brain

in the mammals trated

that

head

showed

the

spontaneous marked

40°C to 20'C, temperature

temperature

has been reported

and

EEG

changes

that

the

was lowered

was lowered

tween

activation

the

EEG

the

surgical

procedures.

von

heating

synchronized

the

rabbit.

Little

nization

and

In the

perfused

of brain,

tympanic induced

by

reported

that

rate

rabbit.

They

increase

in the

tude

of the spontaneous

caused

drowsiness

tympanic feasible

reflexion

The

present

the

brain

the

influence

the

carotid

and inhibited been

of the

temperature of

the

carotid

brain

and

central

cooling

and

and

behavior,

cooling

of the

increase

and

blood

in the

measured

through

in tempera

blood

the external

pressure

arteries

in the

shivering,

in frequency the

and

temperature.

carotid

Further,

rat

on synchro

the changes

while

rate.

be

reports,

in both

of drugs

alerting,

pressure,

heart

when

hypothalamic

respiration,

increase

brain

non-physiological

activity

common

produced

depth,

their

moderate

of brain

rectum,

and

from

extreme

(3) observed

the

correlation

obvious

motor

both

when

the

the influence

cat's from

increased

that

by changes

warming

fell

inferred

Takaori

and

cooling

temperature

experiments

caused

and

frequency

to study

perfused varying

of the EEG

from

(2) showed the gamma

done

of EEG

slight

However,

suffered

artificially

EEG

was not

Soderberg

undulation

and

membrane

presumedly

membrane

respiratory

at temperature

temperature

Tanabe

heart

and

voltage

40°C to 33°C.

and

hitherto

and

isolated

and

cortical

(EEG)

et al. (1) demons

from

voltage

would

ture

Gaenshirt

mean

Euler

reports,

electroencephalogram

of the

desynchronization

previous

the

frequency

brain

EEG

upon

investigators.

to 32°C, while from

head

work has

recorded

mean

and

because

several

in frequency

down

the temperature

changes

by

carotid they

pallor,

and

ampli

warming

regarded

the

canal

as a

auditory

temperature. have

been

the EEG's

depressants

designed

in the and

to elucidate

cortical

stimulants

the

relationship

and

subcortical

on the

EEG

areas,

alterations

between and to trace induced

by

warming. METHODS

One tion 高折

hundred

of the

and fifteen

tracheal

修二 ・田辺

cannula

堅 三郎

male albino and

attaching

rabbits

weighing

the modified

2.0 to 2.5 kg were used. apparatus

of Kahn

Inser

(4) on both

common carotid arteries for the cooling and warming were followed to the methods described in the previous papers (3). The carotid arteries were cooled by irrigating cold water at 5, 15 and 20`C through the metal tubes of the apparatus at a speed of 15 MI/Min for 6 and 60 minutes, and the arteries were warmed by the irrigation of water at 50-C at a speed of 40 ml/min for 8 and 60 minutes. Under ether anesthesia, the head of the animal was fixed on the stereotaxic instrument (Todai-Noken type). The skull was exposed and trepaned for recording the EEG from the motor cortex, hippocampus and hypothalamus. The coordinate used for the subcortical structures were obtained from the histological map of Sawyer et al. (5) : hippocampus (F: -4.5, L : 5.5, H : 5.5) and posterior hypothalamus (F: -1.0, L : 1.5, H : -4.0). Cortical EEG recording was accomplished with a monopolar silver ball electrode placed on the intact dural surface. A monopolar insulated silver electrode, 0.3 mm in diameter, were used for recordings of the deep structures. The indifferent electrode was placed on the frontal cranium. The experiments were performed in a sound-proof room at the temperature of 22±2' C, and were not started at least earlier than 2 hours after the termination of the surgical procedures and ether anesthesia. Electroencephalograph (San'ei Sokki, Type EG-129) and EEG analyser (San'ei Sokki, Type EA-101) were employed. The EEG recorded from the motor cortex was integrated for every 10 seconds into the following groups of wave-band: 2--4, 4-8, 8-15, 15-30, 30-55, 65-100 and 100-150 cps. The mean integrated values of 2-4, 4-8 and 8-15 cps bands were calculated by measuring 5 to 10 consecutive recordings. Respiratory move ments and electrocardiogram (standard limb lead II) were simultaneously recorded. Rectal temperature was measured by the use of thermistor mounted on catheter and fixed at depth of about 6 cm from the anal ring. Tympanic membrane tempera ture was measured by means of thermistor covered with plastic coating. Details of the measurements were previously descreibed (3). In the experiments to exclude influence of the carotid body on the EEG findings, the bilateral bifurcations of the internal and external carotid arteries were carefully exposed and separated from the surrounding tissues. The nerve branches connecting the carotid body with the glossopharyngeal and vagal nerves were cut off. Moreover, 2% solution of lidocaine was applied to the carotid body about 10 minutes before cooling and warming the common carotid arteries. The drugs used were pentobabital sodium, chlorpromazine hydrochloride, reserpine, aminopyrine, sulpyrine, atropine sulfate, methamphetamine hydrochloride, caffeine, pheniprazine (Catron), pipradrol hydrochloride, imipramine hydrochloride and physos tigmine salicylate. They were all injected into the marginal vein of the ear. RESULTS

1.

Effect of cooling and warming the common carotid arteries on the EEG When most of the unanesthetized

fixing the electrodes,

the spontaneous

rabbits

were kept quiet more than 2 hours after

EEG in the motor cortex showed alternately

two

main

patterns:

low-voltage with

fast waves,

spindle

type"

bursts.

by Kikuchi When

mon

cold

carotid

voltage Even the

an arousal

fast though

EEG

EEG

and

the

water

waves

(100-150 during

the EEG

in

desynchronized

high-voltage

to this

through

showing

the

group

slow waves

was named

by

metal

resting

the

tubes

around

was immediately

spindle

long-lasting

pattern

the

cortex

,aV, 20-35 cps) and

showed bands

results

a marked

are

by

shown

cold

bursts

disappeared

pattern stimulation.

The

in the The

slow frequency

/AV, 4-6 cps)

pattern was

stimulation,

posterior carotid

waves

but

by heart

of relatively the

carotid

rate

did

low

completely.

arousal

pattern

removal values

cps-band after

type"),

of of

activities, the

onset

of

9.

hypothalamus cooling

8-15

at 6 minutes

with

consisted water

(40-60 aV, 4-6 cps).

consisted elicited

1, 2 and

60%

com

into

of EEG ("resting

of 2-4, 4-8 and

68, 61 and

in Figs.

EEG

arousal

decrease

decreased

waves.

cold

"mixed

both

altered

6 minutes of the cooling, and also 3 to 5 minutes after the Thereafter, the EEG returned to normal. The integrated

low-voltage

the

presented

of synchronized

belonging

the motor

spontaneous

regular

The former

consisted

of rabbit

to the arousal

frequency

hippocampal

pattern.

at 15°C was perfused

(20-40

respective

irregular tively

EEG

in the animals

These

The

and the latter The

arteries,

changed

cooling.

a resting

(6, 7).

persisted during cold stimulation. the

and

In the

high-voltage cooling. not show

at

of

comparatively

15°C resulted hippocampus, and regular

Respiratory remarkable

rate change.

FIG. 1. EEG alterations induced by the carotid cooling (15°C). MC : motor cortex, Hyp : posterior hypothalamus, ECG : electrocardiogram (II lead), Resp : respiration.

in rela so-called

slow waves increased

FIG. 2. Influence of the carotid cooling (6 minutes) on integrated values of EEG recorded from the motor cortex. Each value represents 2-4, 4-8, 8-15, 15-30, 30-55, 65-100 and 100-150 cps-band activities, respectively.

The carotid in the motor

cooling with water

cortex.

at 5-C induced

a clear-cut

arousal

pattern

of EEG

after the onset of cooling (5°C), the 2-4, 4-8 and by 76, 70 and 73%, respectively. However, a mild cooling with water at 20-C did not transfer the EEG to a typical arousal pattern . Occasionally, the high-voltage slow waves and the spindle bursts appeared during the 8-15 cps-band

cooling.

At 6 minutes

activities

decreased

The 2-4, 4-8 and

depressed

8-15 cps-band

activities

of the EEG were

not markedly

(Fig. 2).

When warm water mon carotid

arteries,

at 50°C was perfused

through

the metal tubes around

the EEG in the motor cortex changed

to high-voltage

both com slow waves

(100-200 ,t V, 1-5 cps) with spindle bursts (50-150 ,"V, 8-15 cps) within 3 minutes after the warming. The resting pattern lasted during 8 minutes of the warming, and also 3 to 5 minutes after the removal of warm stimulation; and then the EEG was restored to the normal marked bands and

pattern

increase increased

(Fig. 3).

The integrated

of the 2-4, 4-8 and by 44, 32 and

11). In the rabbits

values of the EEG frequency

8-15 cps-band

17% at 8 minutes

which showed

showed a

activities , and the respective cps after the onset of warming (Figs . 4

only the arousal

pattern

of spontaneous

("alert type") even though external stimuli were carefully avoided, the carotid sometimes failed to produce the resting pattern. In the posterior hypothalamus

EEG

warming and hip

pocampus, the carotid warming (50°C) caused the pattern of high-voltage and irregular slow waves (100-200 aV, 1-4 cps) accompanied with the disappearance of regular slow waves.

4-8

Fig.

5 shows

and

8-15

the

cps-bands

changes of

of the

tympanic EEG

in

membrane the

motor

and cortex

rectal in

temperatures

response

to

irrigation

and

2-4, with

FIG. 3. EEG alterations induced by the carotid warming MC : motor cortex, Hyp : posterior hypothalamus , ECG : electrocardiogram (II lead), Resp : respiration.

(50'C) .

FIG. 4. Influence of the carotid warming (8 minutes) on integrated values of EEG recorded from the motor cortex. Each value represents 2-4, 4-8, 8-15, 15-30, 30-55 , 65-100 and 100-150 cps-band activities, respectively. cold

(15°C) and

ture

declined

amounted

to

warm

1.85°C at

progression of the was removed, the hand, cooling In

the

the

rectal

and EEG

(50°C) water

immediately

after 20 minutes

temperature tympanic

temperature

the mean recorded

for 60 minutes. the

started

the

after

decline membrane

temperature from

cold

motor

The

stimulation, the

onset

decrease cortex,

the

of cooling .

was observed. temperature

to fall very

tympanic and

slowly

membrane mean

Thereafter,

As soon as the elevated rapidly. but

the

arousal

pattern

no

fall further

cold stimulation On the other

progressively

was 0.63°C at 60 minutes

tempera

temperature

by the carotid after

persisted

the cooling . continuously

and

the

served

resting during

pattern the

4-8

and

8-15

the

EEG

showed

65%.

cooling.

cps-band

Several

ruption

to

The

2-4, of

after

of 40 to the inter

the activities

the

ob

activities

a decrease

minutes

of cooling,

restored

was not

respective

were control

levels. The perature ly after

tympanic

tem

started to elevate immediate the carotid warming (50°C),

and

the

was

1.65'C

onset

mean

of

The

10 minutes

increased

progressively, ture increase 60 minutes

temperature

at

warming.

temperature

tion.

membrane

increase after

the

Thereafter,

the

gradually

and

and the mean tempera amounted to 1.84-C at after

the

tympanic

warm

stimula

membrane

tem

perature turned to decrease immedia tely after the removal of warming. However,

the rectal

temperature

FIG. 5. Relationship between percent integrated values of EEG in the (solid ing.

line)

and

the

carotid

changes of motor cortex

cooling

or warm

start

ed to increase very slowly after the carotid warming and the mean temperature increase was 0.96°C at 60 minutes after the warming. The rectal temperature continued to elevate even after the removal of warm stimulation and showed a tendency of recovery about 30 minutes after the interruption of warming. In the EEG recorded from the motor cortex the resting pattern accompanied with the spindle bursts was observed during the warming. The 2-4, 4-8 and 8-15 cps-band activities of the EEG showed an increase of 40-65, 25-40 and 30-50%, respectively. About 10 minutes after the interrup tion of warming the activities returned to normal. Decentralization of the carotid bodies and local application of lidocaine on the structures did not show any remarkable influence against the spontaneous EEG in the motor cortex and posterior hypothalamus and also against the EEG alterations induced by the carotid cooling and warming. 2. Effectsof drugs on the EEG alterations inducedby the carotid coolingand warming 1) Pentobarbitalsodium The intravenous injection of 5 mg/kg of pentobarbital sodium resulted in the mani festation of slow waves intermingled with spindle bursts and in the marked increase of 2-4 cps-band activity in the integrated value of EEG recorded from the motor cortex. At 10 minutes after the administration, the common carotid arteries were cooled

FIG. 6. Effect of pentobarbital sodium on the EEG alterations induced by the carotid cooling. A, a : before, B : 10 minutes after intravenous injection of 5 mg/kg of pentobarbital sodium, b : 10 minutes after intravenous injection of 10 mg/kg of pentobarbital sodium, C, c : 4 minutes after the onset of carotid cooling (5'C), and D, d : 10 minutes after the interruption of the cooling. by irrigation

of cold

6 minutes.

The

after

cold

(Fig. 6).

the

increased.

the 2-4,

4-8 and

of cooling, values

those

of the On

8-15

hand,

in the

the appearance

induced

a slight

cps-bands

slightly

non-treated

the other

dose

by the

EEG

cps-band

decrease

respectively

were

hibited

(5°C). tivities

of the 30-55

The

sodium

tern

the

39% at 6 minutes

These

into the

The 2-4, 4-8 and

activities

while

activity

onset

the per of the

fast

immediately

60, 54 and

7. Effect of pentobarbital sodium on cent changes of integrated values cortical EEG.

altered

low-voltage

waves

decreased,

FIG.

EEG

pattern

8-15 cps-band

at 5°C for

with

arousal

stimulation

water

in was

after

the

(Fig. 7). less than

animals. pentobarbital

of 10 mg/kg of arousal carotid

in pat

cooling

The 2-4 and 4-8 cps-band ac of the cortical EEG showed decrease

in the range

of 20 to

FIG. 8. Effect of chlorpromazine on the EEG alterations induced by the carotid cooling. A, a : before, B, b : 10 minutes after intravenous injection of 1 mg/kg of chlorpromazine, C : 4 minutes after the onset of carotid cooling (5`C), c : 4 minutes after the onset of carotid cooling (15°C), and D, d : 10 minutes after the interruption of the cooling. Calibration : ordinate 100 "V, abscissa 1 second.

25%, and the 8-15 cps-band

activity

was not depressed by the cold stimula tion (Fig. 7).

2) Chlorpromazine In Fig. 8, it is shown the examples of chlorpromazine on the EEG altera tions induced by the carotid cooling at 5 and 15`C. The intravenous in jection of 1 to 5 mg/kg of chlorpro mazine resulted in an increase of high voltage slow waves consisted of main ly 1 to 5 cps in the motor cortex, as reported previously (8). Following the carotid cooling with water at 5°C at 10 minutes after the administration, the EEG changed from the resting pattern to the arousal pattern. The 2-4, 4-8 and 8-15 cps-band activities

FIG. 9. Effect of chlorpromazine on the percent changes of integrated values of the cortical EEG. C. : Control, Chl.: Chlorpromazine 1 mg/kg.

showed rabbit the

a decrease with

1 to 5 mg/kg

moderate

cps-bands

in the range

cooling

did not

with

show

of 50 to 70% (Fig. 9).

of chlorpromazine water

at 15°C.

an obvious

decrease

prevented The

However, the

integrated

during

and

EEG values after

the pretreatment alterations of the

of the

induced

2-4, 4-8 and cooling

at

by 8-15

15°C.

3) Reserpine The effects of reserpine on the spontaneous EEG in the rabbits were reported by many workers [Rinaldi et al. (9), Gangloff et al. (10) and Kikuchi (6)]. In the present experiments, the intravenous injection of 1 mg/kg of reserpine induced an appearance of slow waves in the motor cortex within 15 minutes after the administration. The slow waves persisted in the first 1 hour, and then the EEG gradually transferred to the mixed type representing alternatively the arousal and resting patterns for 4 hours or more. At 30 minutes after the administration of reserpine, the carotid cooling with water at 5°C resulted in the appearance of arousal pattern. However, the similar pro cedure failed to show the typical arousal pattern at 1, 2 and 4 hours after the drug administration. Figs. 10 and 11 show the changes in the EEG and in the integrated values of 2-4, 4-8 and 8-15 cps-band activities induced by the carotid cooling at 2 hours

FiG. 10. Effect of reserpine on the EEG alterations induced by the carotid cooling and warming. A : before, B : 2 hours after intravenous injection of 1 mg/kg of reserpine, C : 4 minutes after the onset of carotid cooling (5C), D: 10 minutes after the interruption of the cooling ; b : 24 hours after reserpinization (1 mg/kg), c : 6 minutes after the onset of carotid warming (50°C), and d : 10 minutes after the interruption of the warm ing. Calibration : ordinate 100 "V, abscissa I second.

after the administration of reserpine. The high-voltage slow waves remained steady during the cooling, and the 2 4, 4-8 and 8-15 cps-bands showed a decrease in the range of 25 to 35% at 6 minutes after the onset of cooling. Reserpine in the dose of 1 mg/kg was injected intravenously about 20 hours before the surgical procedures for the EEG recordings and for the carotid warming. The spontaneous EEG in the motor cortex showed mainly the desynchronized pattern consisting of low-voltage fast waves 24 hours after the reserpinization. Following the carotid warming with water at 50 C, however, the arousal pattern in the reserpinized animals transferred to the resting pattern, as shown in Fig. 10. The 2-4, 4-8 and 8-15 cps-band activities increased by 48, 29 and

42% at 8 minutes

after

FIG. 11. Effect of reserpine on the percent changes of integrated values of the cortical EEG. C.: Control, Res. : Reserpine 1 mg/kg.

the

onset

of warming,

respectively

(Fig.

11).

4) Aminopyrine and sulpyrine In response

to 25 and 50 mg/kg of aminopyrine,

of the EEG in the motor

cortex

there

(150-300 ,_V, 2-4 cps) lasting

Higher doses above 75 mg/kg resulted in the manifestation seizure discharges.

The resting

occurred

pattern

induced

a resting

pattern

for 20 to 30 minutes.

of slow waves associated with

by the administration

of aminopyrine

(25 to 50 mg/kg) changed easily to the arousal pattern by the carotid cooling at 5 and 15°C. The 2-4 and 4-8 cps-band activities showed a decrease in the range of 60 to 80% at 6 minutes

after the onset of cooling.

Sulpyrine in the doses of 100 to 200 mg/kg produced a resting pattern of EEG in the motor cortex (100-150 ,aV, 2-5 cps) accompanied with spindle bursts lasting for 0.5 to 1 hour.

Following

marked observed.

the administration

of higher

doses up to 400 mg/kg, the EEG showed

slow waves (150-300 1aV, 1-3 cps), and The pretreatment

of the animal

the seizure-like

discharges

were never

with 100 to 400 mg/kg of sulpyrine

did not

prevent the appearance of arousal pattern by the cold stimulation (5 and 15°C) and the appearance of resting pattern by the warm stimulation (50°C). The decrease in 2-4 cps-band cps-band 5)

of the EEG by the cooling by the warming

at 5°C was about

at 50`C was about

60%, and the increase in same

70%.

Atropine

The intravenous

injection

of 2 to 4 mg/kg of atropine

caused a characteristic

EEG

pattern consisted of relatively high-voltage slow waves in the motor cortex. The pre treatment of the animal with atropine pre vented the EEG alterations induced by the carotid cooling with water at 5 and 15°C(Fig. 12). The high-voltage slow waves persisted during the cold stimulation, and the integ rated values of 2-4, 4-8 and 8-15 cps-band activities were not depressed. 6) Methamphetamine Within 5 minutes after the intravenous injection of 1 mg/kg of methamphetamine, the EEG in the motor cortex altered into low-voltage fast waves. The spindle bursts and the slow waves disappeared completely. The EEG recorded from the posterior hypo thalamus showed relatively regular frequency waves. The arousal pattern persisted over 2 hours, and did not change to the resting FIG. 12. Effect of atropine on the EEG alterations induced by the carotid cooling. A : before, B : 10 minutes after intravenous injection of 4 mg/kg of atropine, C : 4 minutes after the onset of carotid cooling (5°C), and D : 10 minutes after the interruption of the cooling. Calibration : ordinate 100 IN, ab scissa I second.

pattern even when the carotid arteries were warmed with at 50°C (Fig. 13). The integrat ed values of 2-4 and 4-8 cps-band activities failed to increase by the warm stimulation (Fig. 14). However, the 8-15 cps-band activity showed an increase of 35 to 45%. The hypo thalamic EEG after the warm stimulation ap peared to be more regular in frequency (40 70 aV, 4-5 cps) titan those before the warming .

7) Caffeine Amounts of caffeine ranging from 20 to 50 mg/kg , injected intravenously, elicited an arousal pattern of EEG in the motor cortex which appeared quickly and lasted for about 1 hour after the administration. At 10 minutes after the injection , the carotid warming (50°C) induced the appearence of slight high-voltage slow waves which persist ed during the warm stimulation (Fig. 13). The 2-4 , 4-8 and 8-15 cps-band activities increased by 15 to 25%. 8) Pheniprazine(Catron) The EEG alterations, consisting of an arousal pattern , were observed 10 minutes after the intravenous injection of 5 mg/kg of pheniprazine , and the arousal pattern lasted for over 6 hours. Following the warm stimulation (50°C) at 2 and 4 hours after the drug administration, the EEG changed from the arousal pattern to the resting pat

FIG. 13. Effect of methamphetamine and caffeine on the EEG alterations induced by the carotid warming. A, a : before, B : 10 minutes after intravenous injection of 1 mg/kg of methamphetamine, b : 10 minutes after intravenous injection of 20 mg/kg of caffeine, C, c : 6 minutes after the onset of carotid warming (50'C), and D, d : 10 minutes after the interruption of the warming. Calibration : ordinate 100 pV, abscissa 1 second. tern.

The

2-4, 4-8 and

activities

8-15 cps-band

increased

by

120,

50

100% at 8 minutes

after

the

onset

warming, 9)

Pipradrol in doses of 1 to 5 mg/kg

no marked

taneous red

of

respectively.

Pipradrol caused

and

EEG,

easily

cps-bands

and

resting

warming values

in the spon

the EEG

to the

the carotid tegrated

change

transfer

pattern

(50°C).

of 2-4,

The

4-8 and

of the cortical

by in 8-15

EEG increas FIG.

ed in amplitude minutes

after

by 40 to 140% the

onset

at 8

14.

Effect

changes

of warming.

C. :

of

methamphetamine

of integrated Control,

on

values

Meth.

:

the

percent

of the cortical

EEG.

Methamphetamine

I

mey/kLy.

10)

Imipramine

The

intravenous

injection

EEG which lasted for about 10 minutes

after

the

of 5 mg/kg of imipramine

caused a resting

1 hour, and then the EEG pattern

administration,

the

carotid

arteries

returned were

pattern

to normal.

cooled

with

of At

water

at 5°C. The EEG changed

from the resting

pattern to the arousal pattern immediately after the cold stimulation. The 2-4. 4-8 and 8-15 cps-band

activities

and 45% at 6 minutes ing,

respectively.

not turn the

decreased

after the onset of coo]

However,

to the typical

moderate

by 69, 54

cooling

the

EEG

arousal with

and the above-mentioned

did

pattern

water

by

at

cps-band

15°C,

activities

showed a decrease in the range of 20 to 40%. When

the

EEG

control pattern tration

had

returned

of imipramine,

the

carotid

were warmed with water at 50°C. changed

to the resting pattern,

cent increase activities

the

arteries The EEG

and the per

in 2-4, 4-8 and 8-15 cps-band

was within the control

11)

to

at 2 hours after the adminis

ranges.

Physostigmine

Amounts of physostigmine

ranging

from

0.025 and 0.05 mg/kg, injected intravenously,

FIG. 15. Effect of physostigmine on the EEG alterations induced by the carotid warming. A : before, B : 10 minutes after intravenous injection of 0.05 mg/kg of physostigmine, C : 6 minutes after the onset of carotid warming (50°C), and D : 10 minutes after the inter ruption of the warming. Calibration : ordinate 100 ItV, ab scissa I second. MC : Motor cortex, Hip : Hippo campus.

elicited a desynchronization

of the EEG

the motor cortex which resembled

in

the arousal

pattern induced by external stimuli. low-voltage fast waves did not transfer

The to a

synchronized pattern by the carotid warm ing with water at 5;;V (Fig. 15). No signi ficant change was observed in the integrated values of 2-4, 4-8 and 8-15 cps-hand activities during

and after the warm stimulation.

DISCUSSION Either EEG's ably

cooling

in the from

the

hemisphere, from

the

arousal

short

cortex,

changes

internal

of the

arousal

directly

the

slow

waves the

waves

also

same

type

and in

rhinencephalon

consisting

between

common

temperature

artery.

of EEG

regular

latency

and

carotid

both

hypothalamus of

diencephalon

pattern

relatively

or warming

motor

The

in the

suggested

the

that

carotid

carotid

as that

mainly caused

activities and

of

the

alertness

by

activated electrical

cerebral

in

The

first detectable

prob

with

in the motor

cooling evoked

derived

supplied

hippocampus.

and the

the spontaneous

effects

structures

were

cooling

procedure the

affected The

various

which

hypothalamus

reaction

arteries

hippocampus.

of desynchronized

onset of cooling

of arousal

carotid

blood

behavior cortex

,

and

extremely appearance

directly

or

stimulation

in of

the subcortical structures and of the peripheral nerves. On the other hand, the carotid warming lead to the appearance of drowsiness, rest ing pattern of EEG consisting of synchronized activity in the motor cortex and com paratively irregular waves in the hypothalamus and hippocampus. The appearance of the behavioral sleep associated with the recruiting response by stimulation of the diffuse thalamic projection system with low-frequency stimuli has been well-known. The similar widespread spindles in the EEG associated with the behavioral sleep were also induced by stimulation of the preoptic region with low-frequency stimuli [Sterman and Clemente (11)]. von Euler and Soderberg (2) showed that the moderate heating of the anterior hypothalamus tended to synchronize the cortical EEG in the rabbit anesthetized with urethane or chloralose-urethane. It has been suggested by Magoun (12) that the mecha nism being capable to drive the synchronized thalamo-cortical system in the hypotha lamus are likely to regulate the innate behavior such as satiety. Several hypotheses have been presented for the explanation of the satiety caused by the activation of the ventromedial nucleus of hypothalamus. According to the thermostatic hypothesis, satiety is brought about through the intermediation of extra heat on this nucleus. This extra heat is presumed to produce an elevation in brain temperature of sufficient magnitude to stimulate certain postulated thermosensitive elements in the hypothalamus. Since cooling or warming the carotid arteries produced the behavioral changes associated with the alterations of EEG pattern, the mechanism was further studied in the present ex periments. The afferent thermo-stimulation reflex mechanism of the carotid body was excluded from the results that the responses of the behavior and EEG to the carotid cool ing and warming were not affected by decentralization of the sinus nerves. Parmeggiani (13) classified the spontaneous sleep behavior into three phases : exploratory and pre paratory, light sleep and deep sleep, by comparing the electrically induced behavioral pattern with the spontaneous sleep in the cat. His conclusions were that the thalamus probably served to coordinate the three phases of the sleep behavior, and that the hip pocampus and related structures subserved to the first phase, the caudate to the second phase and the thalamus to the third phase. He supposed that the sleep occurred depend ing on the integrative action of structures situated at widespread levels in the brain. In addition, the present authors (14) showed in another series of experiments that the electrical destruction of the posterior hypothalamus induced a characteristic EEG pat tern consisting of marked slow frequency waves (1-2 cps) in the motor cortex and hip pocampus, and that widespread destroyment of the diffuse thalamic projection nuclei (Nucl. centralis medialis, Nucl. ventralis anterior and Nucl. reticularis) also resulted in a peculiar pattern consisting of slow waves (2-3 cps) superimposed with fast frequency waves (65-150 cps). Moreover, the authors demonstrated that the destruction of the hypothalamus and the thalamus prevented completely the EEG alterations caused by the carotid cooling and waring. These results suggested that the diencephalon, especially the hypothalamus and thalamus, might play an important role in the EEG changes induced

by

the The

warming dose

ori

cooling

influence are

reserpine

response

EEG 1.

(1 mg/kg)

inhibited

evoked

by

electrical

and

response.

presented

(6), that

The

by

findings

in the

blocked

Partial Complete

pattern", blocking

the

present

effect

blocking

R : "Resting of

EEG of

rabbit

the

pattern",

alterations,

I

appearance

by

experiments

the

(15), Taka EEG

the

showed

but

reticular

their

spontaneous

workers

arousal

formation of

reconfirmed

on the Some

of the EEG

Domino

reticular voltage

and

moderate

(1 to 5 mg/kg)

totally

threshold

cooling with

chlorpromazine

blocked

of reserpine

(6, 9, 10, 16).

alterations,

EEG

the carotid

of the mesencephalic the

experiments.

by

It was described

increased

investigators

while

further

of the

completely

sodium

TABLE

A : "Arousal

induced

stimulation,

stimulation only

demands

pretreatment

it partially.

regarding

many

alterations

pentobarbital

reserpine

reports

cold

problem

The

sodium

by the

Conflicting been

on the

induced

Kikuchi

This

in Table

of pentobarbital

chlorpromazine arousal

warming.

of drugs

pattern

(8) and

and

summarized

(10 mg/kg)

arousal and

carotid

works.

EEG

have

reserpine

elicited desynchronization of EEG, and others described an alternating syndrome of the arousal and resting patterns. Recently, Steiner et al. (17) showed that quite opposite electroencephalographic effects were obtained when reserpine was administered to rab bits prior to surgical preparation for EEG recording as opposed to the drug being given after the rabbit had been prepared for EEG recording. The depletion of catecholamine in the central nervous system as well as in the peripheral adrenergic organs was report ed by several investigators (18, 19). In the present experiments, the resting pattern of EEG lasted for 0.5 to 1 hour after the administration of reserpine. Thereafter, the EEG gradually changed to the mixed pattern which alternated between the arousal and resting patterns. On the other hand, the cortical EEG showed mainly the desyn chronized pattern when reserpine was administered to the rabbit 24 hours before the surgical procedures. However, this desynchronized pattern transferred readily to the synchronized pattern by the carotid warming. These results indicated that the spon taneous EEG in the reserpinized animal could be easily affected by the change of experi mental conditions. It may be a possible reason of the conflicted opinions concerning the effect of reserpine on the EEG. The effects of aminopyrine on the spontaneous EEG were reported by Ban (20). The present results coincided with his works. Sulpyrine, one of the antipyretics, also lead to the appearance of the resting pattern of EEG. However, the seizure discharge did not appear, even though higher doses of sulpyrine were injected intravenously. The results obtained here suggested that the seizure discharges induced by the admi nistration of aminopyrine might have no correlation with antipyretic action of the drug. The synchronized pattern of the cortical EEG by the administration of aminopyrine and sulpyrine changed to the obvious desynchronized pattern when the carotid arteries were cooled down. Rinaldi et al. (21) and Longo (22) showed that slow waves in the cortical EEG were observed following atropine without concomitant changes in behavior, and that the thre shold of EEG activation by electrical stimulation of the reticular formation and the dif fuse thalamic projection nuclei was elevated after the administration of atropine. It was presented in the present experiments that the synchronized pattern caused by injection of atropine was not transferred to the desynchronized pattern by the carotid cooling. The spontaneous EEG showed the arousal pattern in response to the intravenous injection of methamphetamine, caffeine, pheniprazine and physostigmine. The adminis tration of pipradrol, one of the psychic stimulants, failed to show the desynchronized pattern, and imipramine resulted in the synchronized pattern in the cortical EEG. The pretreatment of animals with methamphetamine, caffeine and physostigmine prevented the EEG alterations induced by the carotid warming, while pheniprazine, pipradrol and imipramine did not inhibit them. Kikuchi (6, 7) reported that methamphetamine and pheniprazine caused the desynchronized pattern of the spontaneous EEG and that the threshold voltage of recruiting response was elevated by the administration of metham phetamine but not of pheniprazine.

These results showed that the central stimulating

action of pheniprazine was weaker than that of methamphetamine. The preventing action of imipramine on the desynchronization of EEG induced by the moderate carotid cool ing (15°C) was observed in the same manner as that of chlorpromazine. Kumada et al. (23, 24) demonstrated a resemblance between the effects of imipramine and chlorpro mazine on the EEG in the rabbit. Our findings also confirmed their works. Longo (25) pointed out that there existed a discrepancy between the EEG findings and the behavior of the animal in the case of intravenous injection of physostimine. White (26) emphasized that the EEG arousal mechanism was fundamentally cholinergic in nature. Further studies are required on the relationship between cholinergic mecha nism and EEG activation. McCook et al. (27) showed that the carotid artery flow and hypothalamic tempera ture were inversely related in the cat. Thus, the decrease in brain temperature would be the result of the diminished blood supply to the brain structures, while the increase would be that of the augmented blood supply. Rampone and Shirasu (28) demonstrated that the feeding activity in fasted rats resulted in an immediate increase in brain tem perature and a decrease in rectal temperature. Since the effects did not correlate with any specific property of the diet, the response derived probably from the reflex vaso dilatation caused by widespread shifts in the direction of blood flow during the feeding. Clemente et al. (29) showed that the slow wave synchronous activity in the EEG replaced low-voltage fast activity when the unanesthetized cat received positive reinforcement of food intake, and that these spindles could be abolished by thalamic electrical stimula tion at arousal parameters or by novel auditory stimuli. The evidence serves to show a close correlation between the changes of brain temperature and EEG. SUMMARY The EEG alterations in the motor cortex, hypothalamus and hippocampus induced by cooling and warming both common carotid arteries were studied in the rabbit. Moreover, the effects of central depressants and stimulants on these EEG alterations were investigated. The results obtained were summarized as follows : 1. The carotid cooling (5 and 15°C) elicited the appearance of the arousal pattern of EEG, and the integrated values of the EEG frequency analysis in the motor cortex resulted in a marked decrease of 2-4, 4-8 and 8-15 cps-band activities. On the other hand, the carotid warming (50°C) caused the resting pattern, and the above-mentioned cps-band activities of the cortical EEG showed an obvious increase. The EEG altera tions continued during and several minutes after the cold and warm stimulation. The influence of the carotid body on the changes of EEG caused by the carotid cooling and warming was excluded. 2. Both pentobarbital sodium and atropine completely blocked the appearance of the arousal pattern induced by the carotid cooling, and chlorpromazine and reserpine inhibited it partially. Aminopyrine and sulpyrine failed to prevent it. 3. Methamphetamine, caffeine and physostigmine inhibited the appearance of the

resting

pattern

and imipramine

induced

by the carotid warming,

did not prevent

while pheniprazine

(Catron),

pipradrol

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1) 2) 3) 4) 5) 6) 7) 8) 9) 10)

GAENSHIRT, H., KRENKEL,W. ANDZYLKA,W. : Electroenceph. clin. Neurophysiol. 6, 409 (1954) VONEULER,C. ANDSODERBERG, U. : Ibid. 9, 391 (1957) TANABE, K. ANDTAKAORI, S. : THISJOURNAL14, 67 (1964) KAHN,R.H.: Arch. Anat. Physiol.,Lpz., Suppl.Physiol.Abt., p. 81 (1904) SAWYER, C.H., EVERETT,J.W. ANDGREEN,J.D. : J. comp.Neurol.101, 801 (1954) KIKUCHI,T.: Folia pharmacol.japon. 57, 173 (1961) KIKUCHI,T.: THISJOURNAL11, 151 (1962) TAKAORI, S.: Folia pharmacol.japon. 54, 475 (1957) RINALDI,F. ANDHIMWW'ICH, H.E.: Ann. N. Y. Acad.Sci. 61, 27 (1955) GANGLOFF, G. ANDMONNIER,M.: Helv.physiol.acta 15, 83 (1956)

11) STERMAN, M.B. ANDCLEMENTE, C.D.: Exp. Neurol.6, 91 (1962) 12) MAGOUN, H.W. : The WakingBrain, Second Edition, p. 162,Charles C. Thomas Publisher, Spring field (1963) 13) 14) 15) 16)

PARMEGGIANI, P.L. : Hely.physiol.acta 20, 347 (1962) TAKAORI, S. ANDTANABE,K.: To be published DOMINO,E.F. : J. Pharmacol.115, 449 (1955) GONNARD, P., NECHTESCHEIN, S. ANDSCHMITT, H. : Arch. int. Pharmacodyn. 110, 265 (1957)

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STEINER,W.G., PSCHEIDT, G.R. ANDHIMWICH, H.E. : Science141, 53 (1963) HOLZBAUER, M. ANDVOGT,M. : J. Neurochem. 1, 8 (1956) HIGUCHI,H. : THISJOURNAL12, 34 (1962) BAN,T. : Ibid. 13, 104 (1963) RINALDI,F. ANDHIM\t'ICH,H.E.: Arch. Neurol.Psychiat.73, 387 (1955) LONGO,V.G. : J. Pharmacol.116, 198 (1956) KUMADA, S., HITOMI,M., WATANABE, N. ANDFUKE,H.: Yakugaku-kenkyu 32, 1 (1960) KUMADA, S. : Ibid.34, 298 (1962) LONGO,V.G. : RabbitBrain Research,Vol.2, Electroencephalographic atlas for pharmacological research,p. 35, Elsevier Publishing Co., Amsterdam (1962) WHITE,R.P. : Arch. int. Pharmacodyn. 145, 1 (1963) MCCOOK,R.D., PEISS,C.N. ANDRANDALL, W.C. : Proc. Soc.exp. Biol., N.Y. 109, 518 (1962) RAMPONE, A.J. ANDSHIRASU, M.E. : Science144, 317 (1964) CLEMENTE, C.D., STERMAN, M.B. ANDWYRWICKA, W. : Electroenceph. clin. Neurophysiol. 16, 355 (1964)

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