THE EFFECTS OF THE ADRENOLYTICS ON THE CATECHOLAMINE CONTENT OF VARIOUS TISSUES IN RABBIT

THE

EFFECTS

OF

THE

CATECHOLAMINE

ADRENOLYTICS CONTENT

TISSUES

ON

THE

OF VARIOUS

IN RABBIT

TAKAAKI MATSUO, KEISUKE HATTORI, TAKASHI HONJO AND KIRO SHIMAMOTO Department of Pharmacology, Facultyof Medicine , KyotoUniversity, Sakyo-ku, Kyoto Receivedfor publicationJanuary 13, 1964

In this laboratory, Misu (1) have studied the effects of the adrenolytics on the atrial transmembrane potentials of the isolated rabbit's heart , and have shown that the adre nolytics decrease the rate and amplitude and prolong the total duration of the potentials until the complete disappearance of the potential , and that the abolished potential change is not restarted by the washing-out of the preparation but is restarted by the administra tion of adrenaline or noradrenaline . Theses results prompted the current experiments , in which the effects of the intra venous injection of the adrenolytics such as dibenamine , chlorpromazine and yohimbine on the catecholamine content of the various tissues were studied in rabbits in order to elucidate the mode of action of the adrenolytics . METHODS Intact albino rabbits weighing about 2 kg and of either sex were used. Ten milli gram per kilogram of dibenamine hydrochloride, 5 mg/kg of chlorpromazine hydro chloride and 1 and 5 mg/kg yohimbine hydrochloride were injected into the marginal vein of the ear. Two hours after the injection , the animals were sacrificed by bleeding from the common carotid arteries . Immediately thereafter, the tissues such as brain cortex, brain stem, heart , spleen and adrenals were dissected out and weighed. The tissues were homogenized with 0.4 N-HC1O4 at ice-cold temperature. The extractable noradrenaline and adrenaline were adsorbed to the strong acidic ion exchange resin , Dowex-50W, and were assayed fluorimetrically following the method devised by Carlsson et al. (2). The content of the tissue catecholamine was assayed in some of the spinal animals in which the spinal cords were sectioned between C, and C11and then the doses of the adrenolytics were injected . Since the catecholamine in the tissues except the adrenals mainly consisted of nor adrenaline, the content was estimated as noradrenaline . On the other hand, the content of catecholamine in the adrenals was estimate as adrenaline . The content of the amine in the brain cortex, brain stem and atria was expressed in terms of ,"g/g tissue weight and those in the spleen and adrenals in terms of ,ag/organ. 松尾

高 明 ・服 部

圭 佑 ・本 庄

俊 ・島 本

暉朗

RESULTS

I.

The Normal Content of the Catecholaminein the Tissues

The preliminary estimations of the catecholamine in the tissues of 3 intact rabbits showed the values shown in Table 1. The content of noradrenaline in the brain cortex and brain stem gave considerably uniform values, while the content in the spleen showed much individual variation. However, TABLE 1. The noradrenaline (NA) and adrenaline the estimated values of the catechol (A) contents in the normal rabbit's tissues. amine in the tissues accorded well with those presented by Higuchi et al. (3). II. Effectsof the IntravenousAdministra tion of the Adrenolytics

TABLE 2. Effects of dibenamine hydrochloride 10 mg/kg on the levels of NA and A in the various rabbit's tissues.

TABLE 3. Effects of chlorpromazine hydrochloride 5.0 mg/kg on the levels of NA and A in the various rabbit's tissues.

movements. Though the animals showed and corneal reflexs remained intact. The of the animals 2 hours after the injection noradrenaline in the brain stem showed a 3.

1. Dibenamine The intravenous injection of 10mg/ kg of dibenamine produced a prompt and marked dilatation of the ear vessels and the effect lasted for about 30 minutes. Since the adrenolytic effects of dibenamine were reported to mani fest relatively slow, about 1 to 2 hours after the injection (4), the content of the tissue catecholamine was assayed 2 hours after the injection. Table 2 shows the results. Significantly marked increase was observed in noradrenaline in the spleen. The content of noradrenaline in the atria was also moderately increased.

2. Chlorpromazine The administration of 5 mg/kg of chlorpromazine produced the prompt vasodilatation of the ear vessels and the marked reduction of the spontaneous some signs of the drowsiness, the righting content of the catecholamine in the tissues is shown in Table 3. Only the content of significant increase.

Yohimbine Theintravenous administration of 5 mg/kg of yohimbine evoked violent clonic convulsions, by which some of the animals were killed, within 10 minutes after the injec tion. Some survived ainimals showed a marked respiratory stimulation, -vasodilatation

of the ear vessels, miosis followed with mydriasis and the erection of the penis. The content of the catecholamine in the tissues 2 hours after the injection showed a uniform decrease. But the decrease was significant only in the brain cortex and spleen. Further, the content of the amines in the tissues of rabbits which received 1.0 mg/kg of the drug without manifesting the convulsion is shown in Table 5. The cate cholamine content in all tissues showed decrease and the decrease . was marked in the brain cortex and next in the atria.

TABLE 4. Effects of yohimbine hydrochlo ride 5.0 mg/kg on the levels of NA and A in the various rabbit's tissues.

TABLE 5. Effects of yohimbine hydrochlo ride 1.0 mg/kg on the levels of NA and A in the various rabbit's tissues.

J1I. Effectsof the Adrenolyticson the Contentof Tissue Catecholaminein the Spinal Rabbits 1. Effect of the spinal section The under tive of

spinal

deep procedure

the

Two

the inhalation

catecholamine. show

marked

cortex

and

spleen

showed

of time

anesthesia.

and

tissue

in the brackets ficantly

section was performed

ether

TABLE

percentage of

adrenals. a tendency

the 6.

spinal The

the

The

four

of ether, The

decreases

the

after

the

and

results change

after

the animals are

shown

to the

catecholamine

content

of increase

hours

termination

were

killed

in Table values

content

of noradrenaline

or of diminution

the

the

6, in which

of the were in

for

of the

opera

estimation the figures

intact

rabbits.

Signi

observed

in

brain

the

brain

stem,

of decrease

in accord

tissues

spinal

the atria with

and elapse

section.

contents

of

NA

and

A in

the

various

of

the

rabbits.

2. Effects of the adrenolytics Ten milligrams per kilogram of dibenamine, 5 mg/kg of chlorpromazine and 1 mg/kg yohimbine were injected intravenously to the spinal rabbits 2 hours after the section of the spinal cord. Two hours thereafter, the animals were killed and the dissectcd tissues were subjected to the catecholamine assay. The results are shown in Table 7. The

administration atria

of dibenamine

and spleen

content

in the

affecting

decreased

significantly. atria

and

spleen

the noradrenaline

to yohimbine markedly

the

in the

content

in other

and

content

content

the content

Chlorpromazine the

adrenaline

in the brain

of noradrenaline

spleen

accompanied

of noradrenaline

significantly

content

stem and

decreased with

none

or

in the

decreased in

the

the brain

brain

stem,

the noradrenaline adrenals

cortex.

moderately

in the

less change

of the

without

In response

brain

stem

and

catecholamine

tissues. TABLE

7. and

Effects A in

of

the

the

adrenolytics

various

on

tissues

of

the the

levels spinal

of

NA

rabbits.

DISCUSSION The

administration

of dibenamine

in the adrenolytic

increased the content of the catecholamine only in the spleen.

Benfey

of 20 mg/kg of dibenamine and adrenaline

in the tissues, but the increase

et al. (5) have

found

that

in the urine accompanied secretion

cholamine

in the body.

The increase of the average

the

increased

to the interference

plasma

excretion

concentration

with metabolic

rabbits

was significant administration

of noradrenaline

with the fall of blood pressuree.

the increased

and

the intravenous

in the dog produced the increased

attributed mine

dose to the intact

They have

change of the cate

blood flow of the spleen by dibena

of noradrenaline

in the

cat received

phenoxybenzamine have been shown by Brown et al. (6). Therefore, the increased content of noradrenaline produced by dibenamine is likely to derive from the increased uptake

of the circulating

The

intravenous

adrenaline

about

noradrenaline

administration

30% only in the brain

about 2.3 to 6.7 times of the normal of the drug, as shown by Malhotra and Prasad

stem.

increased

The marked

level, in the brain

noradrenaline

the significant

decrease.

noradrenaline

or serotonin

5 mg/kg Malhotra

(2 to 5 mg/kg) increased

while the lager doses (10 to 25 mg/kg) produced

no significant

was reported

shown that chlorpromazine

of nor

increase of noradrenaline,

et al. (7), was not observed in the rabbits.

markedly,

However,

the content

tissue of dog received

(7) have shown the small doses of chlorpromazine

the dog brain

have

by the spleen, in which blood flow is increased. of chlorpromazine

effect of chlorpromazine

by Gey and Pletscher

modifies

to the various drugs, and that chlorpromazine

the content

(8).

The latter

of the monoamines

inhibits the protective

on the tissue authors

in response

effect of iproniazid

on the release of the monoamines induced by reserpine. The mode of action of chlor promazine has been suggested by the authors to derive from the decreased permeability of the storage organelle to the monoamines since chlorpromazine does affect neither MAO (monoamine oxidase) or DCO (decarboxylase of aromatic amino acid) nor the penetration of iproniazid and reserpine into the tissues. The assumption was further substantiated by the results of Axelrod et al. (9) who have shown that chlorpromazine depresses the uptake of noradrenaline 3H by the tissues, while it does not release the endogenous noradrenaline. The intravenous injection of 5 mg/kg of yohimbine elicited the clonic convulsion in the intact rabbits and some of the animals were killed. The content of the cate cholamine in the tissues of the survived animals showed a decrease and the decrease was marked in the brain and spleen. In order to exclude the possbility of decreasing of effect derived from the convulsion, 1 mg/kg of yohimbine which did not produce convulsion was injected to another series of the animals. The non-convulsant dose of yohimbine also produced the considerable of the content of the amines in all the tissues tested. Therefore, it is likely that yohimbine releases the catecholamine in vivo. There remains the possibility that the effects of the adrenolytics on the content of the tissue amines derive from some central effects. To exclude the possibility the effects of the adrenolytics on the spinal animals were further studied. The spinal cord section decreased the amine content by about 30% in the brain cortex and adrenals and slightly in the brain stem. Four hours after the section the noradrenaline content in the atria and spleen turned to some increase. The release of the catecholamine from the adrenals to the circulating blood is regarded to be regulated centrally via the splanchnic nerves. The section of the splanchnic nerve (10) and the spinal cord (11) or the administration of the ganglion blocking agents (12) have been reported to decrease the release of catecholamine from the adrenals by reserpine. The depletion of catecholamine in the adrenals by insulin was also shown to be of central origin (13, 14). The slight but significant re-increase of the amine in the atria and spleen 4 hours after the sur gical procedure may derive from the uptake of the circulating amine through the weak barrier mechanism for penetration. The administration of the adrenolytic did not significantly affect the content of the catecholamine in the brain cortex of the spinal rabbit. The marked decrease of the noradrenaline content in the brain cortex of the intact rabbits produced by yohimbine was annuled by the spinal section. The spinal section turned the none effect of dibena mine on the content of noradrenaline in the brain stem of the intact rabbits to the moderately marked decrease, the increasing effect of chlorpromazine to no change, and the procedure did not affect the effect of yohimbine. The slight increase of the nor adrenaline content in the atria of the intact rabbit caused by dibenamine and chlor promazine was turned to the decrease by the spinal section, while the reduction of the noradrenaline content produced by yohimbine was annuled. The spinal section poten tiated the decreasing effect of the adrenolytics on the noradrenaline content in the spleen

or. turned content

the increasing

effect to the decreasing

in the adrenals

the procedure

by chlorpromazine

did not significantly

et al. (15) have

reported

that

one.

The decrease of the catecholamine

was potentiated

by the spinal section, while

affect the effect of dibenamine

the adrenolytics

including

and yohimbine.

dibenamine,

Benfey

chlorpromazine,

phenoxybenzamine and phetolamine stimulate the heart in the spinal dog or cat and the stimulating effect was prevented by the previous reserpinization of the animals. They have suggested

that the adrenolytics

the release of the endogenous

inhibit

and

in some structures

showed the adrenolytics

Consequently,

in the tissues derives stantiated

by the central

section results

in the marked

the passive accumulation

nervous

system.

in the manifestation

nolytics by abolishing

increased

the content

depletion

of catecholamine

it is much likely that the increase of the catecholamine

from

of

such as spleen and brain stem of the intact animals,

that the spinal cord section resulted

the tissues.

effect in virture

catecholamine.

The results in the current experiments of catecholamine

the stimulating

or active uptake

Further,

it is assumed

of the catecholamine

the accumulation

or uptake

in

content

mechanism

sub

that the spinal cord

releasing

effect of the adre

mechanism.

SUMMARY The amine

effects of the intravenous

content

of the adrenolytics

in the tissues were studied in the intact

1. In the intact

rabbits

the tissue catecholamine intravenous

administration

the administration

and the increase

administration

was significantly

noradrenaline

content

other tissues.

On the other hand, the administration

the content of the catecholamine adrenals uniformly.

in the brain

adrenaline

The

in the brain

catecholamine

content

administration stem. in the

content

rabbits

in response

brain

in the spleen. the increase

a significant stem, atria,

The of the

change

in

decreased spleen and

in the brain cortex and adrenals

content

of dibenamine

The spinal spleen

increased

of 1 mg/kg of yohimbine

cortex,

was reduced by about 30%, while the noradrenaline increased.

marked produced

stem by about 30% without

2. In the spinal rabbits the catecholamine slightly

and spinal rabbits.

of 10 mg/kg of dibenamine

of 5 mg/kg of chlorpromazine

in the brain

on the catechol

in the atria and spleen was

decreased

the content

showed a marked to the adrenolytics

of nor

reduction

of the

studied.

Some

reduction of the noradrenaline content in the atria was found in response to dibenamine and chlorpromazine. No significant change of the content of catecholamine in the brain cortex and adrenals of the spinal rabbits tion of the adrenolytics.

was observed

by the intravenous

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administra

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