Apomorphine hypothermia: Diminution by group motor excitation and by tricyclic antidepressants, adrenergics, and neuroleptics

Apomorphine Hypothermia: Diminution by Group Motor Excitation and by Tricyclic Antidepressants, Adrenergics, and Neuroleptics

IZYASLAV P. LAPIN

AND

SAID MIRZAEV

In grouped male rats (Wistar and random bred) motor excitation counteracts apomorphine hypothermia. This is not true for grouped male mice (SHR). For this reason the dose-response curves for apomorphine hypothermia differ in isolated and grouped rats but not in mice. The fall of temperature produced by apomorphine at all doses tested is much greater in mice than in rats. Ten imipramine-like inished

antidepressants,

apomorphine

three

hypothermia

adrenergic in

drugs,

and

six

neuroleptics

dim-

rats.

The antiapomorphine effect of imipramine and desmethylimipramine is greater and more easily reproducible in rats than in mice. Apomorphine hypothermia in rats can be used as a reliable test for psychotropic drugs. Key Words: roleptics

Apomorphine;

Hypothermia;

Rat; Mouse; Antidepressants;

Neu-

INTRODUCTION Apomorphine

(AH)

hypothermia

has been

described

in mice (Lapin and Samso-

nova, 1968a) after administration by various routes (ip, SC, intraventricularly). Both tricyclic antidepressants and neuroleptics were found to antagonize it in mice (Lapin and Samsonova, 1968a, Lapin, 1969). AH was then proposed as a test to differentiate Later AH Barnett

antidepressants

from

ineffective

in mice was again described

anticholinergics

in the literature

et al., 1972) and the efficacy of some antidepressants

demonstrated.

It was suggested

antidepressants

is related to an adrenergic

of butyrophenone stimulated

(Fuxe and Sjdqvist,

neuroleptics

by apomorphine

1968).

and Sjoqvist,

1972,

and neuroleptics

1972) that antagonism

was

of AH by

effect of these drugs and that antagonism

was due to a blockade

(A). The

(Schelkunov,

(Fuxe

involvement

of dopamine

of brain noradrenaline

receptors in the AH

in mice was demonstrated (Schelkunov and Stabrovsky, 1971), and most recently further evidence has been reported (Schelkunov, 1977) both for the role of brain noradrenaline In rats AH Wurtman, From ingrad,

and the use of AH as a very sensitive test for psychotropic drugs. has been observed in numerous studies (Kruk, 1972; Yehuda and

1972;

Grabowska

the Laboratory

et al., 1973a;

of Psychopharmacology,

Grabowska,

Bekhterev

1976).

Although

Psychoneurological

Research

AH

in rats

Institute,

Len-

USSR.

Address neurological

reprint

requests

Research

to:

Institute,

Reported

at the Meeting

Received

September

Prof.

I.P.

Leningrad

Lapin,

Laboratory

193019,

of the Pharmacological

of Psychopharmacology,

Society,

22, 1978; accepted October

Bekhterev

Psycho-

USSR. Leningrad,

February

8, 1977.

17, 1978. 127

@lsevier

North Holland,

Inc.. 1979, Journal of Pharmacological

Methods

2, 127-134 (1979)

0160-5402/79/02012708$02.25

128

lzyaslav P. lapin and Said Mirzaev did not differ is not dose

markedly

from

dependent

that in mice, there

in mice (Lapin

1973a) but is in rats (Grabowska

et al., 1973a);

alter brain serotonin concentration bowska et al., 1973a); LSD reverses mice (Lapin,

1971;

Grabowska

are some dissimilarities;

and Samsonova,

1968a;

in mice, apomorphine

do not antagonize

precisely

et al., 1973a).

AH. This

et al.,

(A) does not

while in rats, A elevates it significantly (GraAH in rats (Grabowska et al., 1973a) but not in One

more

recently (Crabowska, 1976). In this paper the presented in contrast to the mouse, antidepressants (imipramine, tyline)

e.g., AH

Grabowska

intriguing

AH in rats and in mice with

finding

particular

difference

was reported

data show that in the rat, chlorimipramine, nortrip-

impelled

emphasis

us to compare more

on the effect of antide-

pressants. METHODS The present the methods

study attempts

to reproduce

are based on those

data reported

described

by Grabowska

by Grabowska

(1976), and

et al. (1973a).

Animals Male Wistar

rats

(110-160

g), random-bred

albino

rats (120-180

mice SHR (bred from Swiss) of both sexes (18-22 g) from used. Rats and mice were housed in a vivarium in groups respectively. boxes,

In the

respectively,

placed in boxes, and 8 mice,

laboratory, 6~6x10

respectively,

devoid

isolated

mice

and rats

cm and 35x24~19 20x15x10

of food

g), and albino

Rappolovo farm were of 20 and 50 animals,

were

cm; grouped

placed

in wooden

mice and rats were

cm and 51 x51 x20 cm. Groups

and water,

were

used

for

each dose

of 6-8 level

rats

during

experimentation. Drugs Apomorphine

was injected

as an aqueous

solution

prepared

immediately

prior

to administration. Apomorphine was injected ip or SC in a dose volume of 1% (mice) or 0.1% (rats) of the body weight. Other drugs were injected in rats ip 30 min prior

to A in a volume

0.1%

of the body weight.

their effect on body temperature; in doses tested, 30, 60, and 120 min after injection.

All drugs

were controlled

for

none changed body temperature

Body Temperature Rectal

temperature

was

measured

by a medical

electrothermometer

Body temperature was measured prior to injection of A or drug (initial Because AH was maximal and then 30 and 60 min after injection. injection

of A, the difference

temperature

(At,,,) was chosen

then calculated. Student’s t-test. conducted

between

the temperature

as a measure

of AH.

30 min after A and initial

Mean values

of AH?SE

Statistical significance of differences was determined Room temperature was 21-22°C in all experiments,

between

10~~ and ~PM from October

TPEM-1.

temperature) 30 min after

1976 to February

were

according to which were

1977.

Apomorphine

Hypothermia

129

RESULTS

Measurements

of body temperature

prior

to and after injection

of A and other

drugs showed that individual differences in rats are much smaller than in mice. For this reason the standard errors are also smaller and differences between the means are statistically Comparison Wistar

more significant than for experiments on mice. of the effect of A on body temperature in isolated

rats showed

was not true

that AH can be registered

for random-bred

rats (Fig. 1). In grouped

ence of AH on dose was evident of A resulted in disappearance excitation

of the grouped

only in isolated

(Fig. 1). This

random-bred

rats depend-

only up to 5 mg/kg. Further increases in the dose of AH, and this was associated with locomotor

animals

(Fig.

1). Aggressive

breaks of aggressive attacks were often observed. A (IO mg/kg) in isolated and grouped random-bred only in isolated more sensitive

and grouped

animals

vertical

Comparison rats showed

postures

and out-

of the same dose of that AH was present

animals (Fig. 2). Wistar rats appeared to be less sensitive to AH and to the locomotor stimulating effect of A compared with random-

bred rats. In mice, animals tered

the degree

(Figs. in order

of AH

was practically

1 and 2), even in experiments to produce

marked

the same in isolated where

excitation

high doses

(“apomorphine

and grouped

of A were adminisgroup

toxicity”)

in

grouped mice (Fig. 2). Threshold doses (1-2 mg/kg) of A did not differ in rats and mice (Fig. I), whereas the degree of AH after doses of 1, 2, 5, and 10 mg/kg was

FIGURE

1.

grouped

rats and mice.

(W) Wistar;

Dose-response (M) mice:

doses of apomorphine

relationship

(i) Isolated (m) males,

animals; (f) females.

hydrochloride

of 8 mice or 6 rats in control animals after apomorphine. (*)f < 0.05; (00)

for

apomorphine

(g) grouped Numerals:

in mg/kg.

hypothermia

animals; Roman,

Black columns:

in

isolated

(R) rats: (C) random experiment mean

number;

and bred;

arabic,

AT,,, values for groups

receiving distilled water. White columns: AT,, P < 0.02; (eee) P < 0.01; (@eee) P < 0.001.

values

130

lzyaslav

P. Lapin and Said Mirzaev

jcu BN

At'

iCRgz iM

I

t2-

...l ::l-r .:: IO

FIGURE mice

2.

Comparison

of apomorphine

in the same experiment.

much

greater

fU

f0

hypothermia

All animals

in mice than

.M

Lnr&

&

are males.

IO

100 fO0

in isolated

Other

and

symbols

grouped

rats and

as in Fig. 1.

in rats (Figs. 1 and 2). Dependence

of AH on dose was

observed in mice within a dose range of 0.5-2 mg/kg, sometimes 0.5-5 mg/kg (Fig. 1). Further increase of the dose did not result in augmentation of AH (Fig. 2 vs Fig. 1). In isolated kg (Fig. I),

mice,

a sex difference

the same being

both sexes. All imipramine-like was inactive 10 mgikg.

was not observed

true for our previous

antidepressants

at a standard

tested diminished

dose of 5 mg/kg

The antidepressants

were

in grouped

almost

equally

active

4234 ;

::

CT 6

uu :* ::

9

I

and grouped

$

2

2; 7:. 9

A at a dose of

in isolated

ri

-I-

mg/

mice of

AH in rats (Fig. 3). lprindole

(Fig. 3) but it antagonized

8;

At” +4-

in AH at doses of 0.25-2

observations

IO

3 4

i_u

I :*

7

2 iI_

:.

:

;

-2-

FIGURE

3.

Diminution

and grouped White

columns:

columns: phine.

AT,,

AT,, values

Antidepressants:

triptyline;

of apomorphine

rats. Black columns: values after

after

distilled

by tricyclic

after two injections

water

an antidepressant

(1) imipramine;

(5) chlorimipramine;

(10) iprindole.

hypothermia

AT,, values

(ip)

of distilled

+ apomorphine

(all drugs

at a dose

(2) desmethylimipramine;

(6) dibenzepin;

antidepressants

(7) maprotyline;

(5 mg/kg,

of 5 mg/kg,

in isolated

water

ip) + apomor-

(3) amitriptyline; (8) azaphen;

(ip + SC).

SC). Dotted (4) nor-

(9) doxepin;

Apomorphine

I iI

131

.i

x

“‘3

Hypothermia

4567

:P I--+ FIGURE

4.

renergic

Diminution

drugs

apomorphine.

Drugs

zoquinazoline (3) cocaine tyzine

of apomorphine

and inefficacy

(5 mg/kg,

derivative

hydrochloride;

rats. Their activity

AW

hydrochloride;

hypothermia

of anticholinergics. ip;

except

151129;

antagonism

sulfate;

+ distilled

Other

to AH was not associated

AT,,

sulfate,

(5) scopolamine

hydrochloride.

random-bred

columns:

DL-amphetamine

(*) amphetamine

(4) atropine

(7) parpanit

in grouped

Dotted

symbols

with

values

rats by adafter

0.5 mg/kg):

water;

drug

+

(1) imida-

(2) amphetamine;

hydrobromide;

(6) benac-

as in Figs. 1 and 3.

any visible

change of motor

of animals.

Summing

up the results

of all experiments

on rats and mice carried

out during

the present study, we found that the diminution of AH produced by imipramine and desmethylimipramine is much more easily reproducible in rats than in mice (Table

1). Although

in our experiments

desmethylimipramine tically

significant

a dose of 5 mg/kg of both imipramine

proved to be optimal decrease

in AH

was observed

experiments, respectively. The adrenergic drugs DL-amphetamine, i.e.,

they had an antiapomorphine

for antagonism only

cocaine,

effect stronger

and

of AH in mice, a statis-

in about

and AW

25%

151129

and 50% reversed

of AH,

than that of the antidepressants

(Fig. 4). Higher doses of DL-amphetamine alone produced hyperthermia and therefore we gradually lowered the dose of this drug to 0.5 mg/kg which itself was inactive.

Anticholinergics,

except scopolamine,

were inactive against AH. The dose

of scopolamine (5 mg/kg) which antagonized AH tended to raise body temperature in controls, smaller doses of scopolamine proved ineffective.

L

at” +4-

FIGURE

5.

roleptics. Drugs (0.1);

Diminution Dotted

(mg/kg

ip):

(I)

(4) chlorprothixen

as in Figs. 1 and 3.

of apomorphine

columns:

ATSo values

haloperidol (0.1);

sii_

-77

4 2 34

5

hypothermia after

(0.002);

in grouped

a neuroleptic (2) thioproperazine

(5) chlorpromazine

6

random-bred

+ apomorphine (0.002);

(1); (6) perphenazine

rats by neu(5 mg/kg,

ip).

(3) trifluoperazine

(0.01).

Other

symbols

132

lzyaslav

P. lapin

and Said Mirzaev

TABLE 1

Reproducibility

lmipramine

of the Antiapomorphine

and Desmethylimipramine

Effect of

in Rats and Mice

ANTAGONISM OF APOMORPHINE HYPOTHERMIA (No. Animal SPECIES Rats (random

IMIPRAMINE

DESMETHYLIMIPRAMINE

a/a

12112

4115

14124

bred)

Mice (SHR) Groups injected

of 6-8

Numerator:

number

Denominator:

Neuroleptics effective doses zine)

male

animals.

ip at a dose of 5 mg/kg

lmipramine

and

30 min prior

of groups

total number

of

Groups)

with

of groups

desmethylimipramine

were

to apomorphine.

significantly

diminished

hypothermia.

tested.

in small doses diminished or prevented AH (Fig. 5). The minimal of specific neuroleptics (haloperidol, thioproperazine, perphena-

were very small-0.002,

0.002 and 0.01 mglkg,

respectively.

DISCUSSION

In spite of the less profound AH in rats compared with mice (Figs. 1 and 2) there was much less individual variation, and the differences in AH between control and drug-treated

groups

were

more

often

statistically

significant

(Figs.

3-5).

The

rat

therefore seems to be the species of choice. In addition, our previous studies have demonstrated rats to be preferable to mice in antidepressant screening using reserpine

because in mice not only antidepressants

reserpine

hypothermia

(Lapin,

but anticholinergics

antagonize

1968).

AH was not seen in grouped Wistar rats at any of the doses tested (0.5-10 mg/ kg). In contrast there was a dose-dependent AH in isolated animals. This difference suggests that stimulation of locomotor activity in grouped rats counteracts AH. The motor

activity

was, however,

agreement with previous isolated Wistar rats when produced

a uniform

One can suggest in motor

increase

therefore

activity.

similar

after all doses

in activity

(Grabowska

that AH in isolated

It has already been shown

be associated

with

and CC57BR)

locomotor

of A, this

observation

results from precise measurements it was demonstrated that, in doses

decreased

(C3H/A),

activity

et al., 1973b;

rats develops

increased

again suggesting

(C57BL/6)

Maj et al., 1972).

independent

in mice of different

being in

of locomotion in of 0.2-10 mg/kg, A

strains

of changes that AH can

or unchanged

that AH and inhibition

(BALB/c of motor

activity are not causally related (Lapin, 1975). The disappearance of AH in grouped random-bred rats with gradual increase in dose of A (Fig. 1) could explain the failure to register AH in the rat following doses of about IO mg/kg and higher, and may account for why the phenomenon of AH was previously

described

only in the mouse

(Lapin and Samsonova,

1968a) and not

the rat (Lapin and Samsonova, 1968b). Our observation that AH after a threshold dose of 1 mgikg is significantly greater in mice than in rats (Fig. 1) agrees with data reported elsewhere (Grabowska et al.,

Apomorphine 1973a). doses

However,

this

of A also

species

difference

and in this

respect

previous authors. Dependence of AH on dose (Figs. previous

observations

(Lapin

was seen

differed

in the present

from

the

1968a;

study

results

1 and 2) was observed

and Samsonova,

Hypothermia at higher

obtained

by the

in mice in contrast

Crabowska

133

et al.,

to

1973a).

However this was evident only at a low dose level within a narrow range (0.5-2 mg/ kg) and consequently these doses are more suitable for studies of effects of drugs on AH than higher A consistent

supra-maximal

reproducible

doses

rats is documented

in the present

nortriptyline

were

which

even quantitatively, (s) for disagreement ucibility

inactive

here speaks

of antidepressants

by all ten tested

study.

antidepressants

Even imipramine,

in the study

of AH in

chlorimipramine,

of Grabowska

and

(1976) did not differ,

from the other antidepressants studied. Although the reason between the two studies remains unknown, the good reprod-

of the antagonistic

reported

of A.

antagonism

effect of antidepressants

against AH at the dose levels

in favor of a choice of rats against mice for studying

the effect

on AH and its mechanism.

The high efficacy of adrenergic drugs in antagonizing AH in rats is similar to that reported elsewhere for mice (Lapin and Samsonova, 1968a; Schelkunov, 1968,1977), and this

lends

mechanism

support

to the idea that noradrenaline

of antagonism

essentially

similar

reserpine,

reserpine-like

by tricyclic

antidepressants

to the hypothermia drugs,

induced

a measure

of their

for them patients.

and not

The

inactivity

adrenergic sufficient

by a variety

5-hydroxytryptophan,

counteracts the fall of body temperature. the antagonism by tricyclic antidepressants activity for

has a control of AH.

of anticholinergics,

role

in the

respect,

of other

where

AH is

agents,

adrenergic

e.g.,

activation

It therefore seems most probable that of AH in both rats and mice is primarily

and, consequently,

predicting

In this

this

thymoanaleptic

even in doses

which

effect is not specific activity

in depressed

far exceed their

normal

anticholinergic dose levels, suggests that AH can be used to differentiate antidepressants from anticholinergics in the rat as well as in the mouse (Schelkunov, 7968). Finally

since the minimal

effective

doses of neuroleptics

in the rat were lower than those reported 1977), it would appear that the rat provides neuroleptic

apomorphine

necessary

to reduce AH

elsewhere for the mouse (Schelkunov, a more sensitive model in the study of

interactions.

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