Cataleptic state and hypothermia in mice, caused by central cholinergic stimulation and antagonized by anticholinergic and antidepressant drugs

Int, 3. Neumphornraol., 1968,7,325-335 Pergamon Press. Printedin Cit. Britain.

CATALEPTIC STATE AND HYPOTHERMIA IN MICE, CAUSED BY CENTRAL CHOLINERGIC STIMULATION AND ANTAGONIZED BY ANTICHOLINERGIC AND ANTIDEPRESSANT DRUGS G.ZETLER lnstitut ftir Pharmakologie,MedizinischeAkademieLiibeck, Liibeck,Germany

(Accepted3 November1967) Summary-A cataleptic state in mice is produced by arecoline,pilocarpine, tremorine,nicotine, and paraoxon. To protect the animals against the peripheral actions of these cholinergics, atropine methylnitrate was given before the first three drugs, hexamethonium bromide before nicotine, and pralidoxime before paraoxon. Atropine, scopolamine, imipramine, desipramine, and amitriptyline prevented catalepsy. This antagonistic action was dose-dependent, scopolamine being at least 10 times more active than atropine. Desipramine was less active than imipramine. With the exception of nicotine, cataleptic doses of the choline&s also caused hypothermia which was diminished or abolished by atropine and scopolamine, the latter being, ~tica~leptic doses of the antidepress~ts however, inactive against tremorine h~thermia. did not influence hypothermia. It is concluded that (a) muscarinic stimulation of the central nervous system causes catalepsy and can cause hypothermia; (b) catalepsy and hypothermia are independent phenomena. INTRODUCTION

THE CATALEPTIC activity of neuroleptic drugs, first observed by COURVOWR etal. (1957), is antagonized by centrally acting antichol~nergics and by antiparkinson drugs (ZETLER, 1960; ZETLER et al., 1960; SC~AU~ANN and KURBJ~~, 1961;MORPURGO, 1962; TAEKHLER et al., 1962; LESLIE and MAXWELL, 1964; MORPURGO and THEOBALD,1964; MORIWRGO, 1965; RIBBENTROP and SCHAIJMANN,1965). Tricyclic antidepressants are also antagonists of neuroleptic-induced catalepsy in laboratory animals (ZETLER,1960; ZETLERet al., 1960; THEOBALD et al., 1964; RIBBENTROPand SCHAUMANN, 1965; MILLER NIELSENet al., 1966; THEOBALDet al., 1966). These antidepressant drugs have central anticholinergic potency (TOMAN,1963; SULSERet al., 1964; BENESOVA et at., 1964; HERZ, 1965; LOEW and TAESCHLER, 1965; S~HAU~NN and RIBBENTROP,1966). Thus, the common denominator of these anticataleptic effects is probably a central anticholiner~c mechanism of action. These findings point to the possibility that the cataleptic action of neuroleptic drugs originates from an activation of cholinergic processes or from a predominance of cholinergic mechanisms. Therefore, it seemed necessary to investigate whether centrally acting cholinergic drugs can produce a cataleptic state which is antagonized by anticholinergic and antidepressant drugs. Hypothermia, too, can be caused by centrally acting cholinergics (EVERETTet al., 1956; MAICKELet al., 1964; SPENCER,1965; LOMAXand JENDEN,1966; MORPURGO,1967) and prevented or reversed by anticholinergics and imipramine or desipramine. Since 325

326

G.

ZETLER

hypothermia is possibly linked to or caused by the state of akinesia (LESSINand PARKE& 1957; BASTIAN,1961) and inhibits central nervous functions in mice (SUDAKand ESSMAN, 1962; ESSMANand SUDAK, 1963), this paper describes also the changes of body temperature during the experiments. Arecoline, pilocarpine, tremorine, the cholinesterase inhibitor paraoxon, and nicotine were used for cholinergic stimulation of the central nervous system. The strong peripheral actions of these drugs would cause indirect central effects consecutive to bronchial and intestinal spasms (diarrhoea), severe salivation and circulatory reactions, and had therefore to be suppressed by the following peripherally-acting antagonists. Methylatropine which was combined with arecoline, pilocarpine or tremorine, penetrates the blood-brain barrier very slowly (VERNIERand UNNA, 1956; PFEIFFERand JENNEY, 1957); its central anticholinergic activity in the mouse is about 600 times weaker than that of atropine (HERZ et al., 1966). It is therefore clear why in contrast to atropine, methylatropine has no anticataleptic potency (ZETLER et al., 1960). Methylatropine and methantheline suppress the peripheral actions of tremorine but do not influence its central effects, hypothermia and anergia (EVERE-~T,1964). Pralidoxime (PAM), a reactivator of the acetylcholinesterase, was used in the paraoxon experiments since little penetrates to the brain (HOBBIGER,1957; KEWITZ and NACHMANSOHN, 1957; RUTLAND, 1958; EDERY and SCHATZBERG-PORATH, 1959; HOBBIGERand SADLER,1959; ERDMANN,1965; FLEISHERet al., 1967) and thus, if given with paraoxon, permits cholinergic stimulation limited to the central nervous system (RIBBENTROPand SCHAUMANN,1965). Finally, hexamethonium was used because of its poor penetration into the brain (PATONand ZAIMIS, 1952; GINZEL, 1967) to protect the animals against the strong peripheral actions of nicotine (LAURENCEand STACEY,1953).

METHODS Animals

Male albino mice, 18-25 g in weight and of the NMRI-strain, were kept in groups of 25 at an ambient temperature of 23°C. The experiments were performed in the same room at the same temperature. Each animal was used only once. In order to eliminate possible influences of the circadian rhythm on the activity of the animals, one half of each experiment was performed in the forenoon and the other half in the afternoon. Experiments

During the experiment, each mouse was seated in a glass cylinder on a petri dish covered with filter paper. The test procedure consisted of putting the animal gently in a headupwards position on a vertical string-wrapped rod and observing it for 50 set (ZETLERand Moot, 1958; ZETLERet al., 1960; ZETLER, 1963). The result was positive if there were no running movements in any direction for at least 30 sec. Within a normal period of observation the mouse was tested every 5 min and considered to be cataleptic if it yielded at least 5 out of 13 possible positive results. The observation was started 10 min after the last injection and lasted 60 min. In the experiments with paraoxon, tremors and muscular weakness retarded the start of observation which began 35 min after the last injection. Each animal received several injections at times indicated by headings of tables and table columns. The body temperature of the animals was measured by means of an electric thermometer and a thermocouple introduced about I5 mm into the rectum before the first injection, i.e. immediately after the animals were transferred into the cylinders, and at

Catalepticstate and hypothermiain mice the end of observation. statistically compared.

The means of the differences between both measurements

327 were

Statistics

The experiments on catalepsy yielded quanta1 responses and were evaluated by means of fourfold contingency tables applying the correction of Yates for the computation of x2. However, the “exact method” of Fisher was used when the value zero appeared in one box of the table. The difference from zero of each mean intra-individual change in body temperature was checked by means of the t-test. It was, however, not possible to compare statistically two means of temperature changes using the t-test if the F-test had revealed significant differences between the variances of the two means. In those cases, the twosample rank test was applied. Differences between groups or means were considered statistically significant if P was < 0.05. Drugs

The following drugs were used dissolved in saline: Atropine sulphate, scopolamine hydrobromide, methylatropine (atropine methyl nitrate, Bayer), paraoxon (diethyl4-nitrophenyl phosphate, Bayer), pralidoxime (pyridine-Zaldoxime methiodide, Bayer), pilocarpine nitrate, nicotine bitartrate, arecoline hydrochloride (Fluka), imipramine hydrochloride (Geigy), desipramine (desmethylimipramine hydrochloride, Geigy), amitriptyline hydrochloride (Tropon). Doses refer to the salts. RESULTS 1. Catalepsy due to paraoxon Pilot experiments not included in Table 1 revealed that after 1 mg/kg of paraoxon S.C. combined with saline solution i.p. all animals showed tremors, muscular fibrillation, severe salivation, prostration and died within 15-45 min. Twenty mg/kg of atropine or 2 mg/kg of scopolamine, given i.p. simultaneously with paraoxon, protected 9 out of 10 animals from death, but muscular weakness prevented the correct performance of the experiment. The body temperature of these mice fell by 4*5-4*9”C during observation time. After the combined application of paraoxon and PAM, mice did not develop salivation and clung to the rod despite tremor which was most pronounced during the first 20 min after injection. All of these animals were cataleptic, and high doses of anticholinergic drugs were necessary to abolish this effect. In this respect, scopolamine was about 10 times more active than atropine. Another difference in activity between atropine and scopolamine, albeit in reverse order, was seen in these experiments, atropine antagonizing hypothermia at a dose still inactive against catalepsy and scopolamine not preventing hypothermia at a dose with full anticataleptic activity. The next experiments (Table 2) revealed that atropine and scopolamine have about 4 times greater anticataleptic activity when given 20 min before the paraoxon-pralidoxime combination. Scopolamine was at least ten times more active than atropine which, again in contrast to scopolamine, antagonized the hypothermia and was active even in a dose too small to be anticataleptic. The antidepressant drugs imipramine, desipramine and amitriptyline were also anticataleptic but less active than atropine. Clear quantitative differences between these drugs were obvious, no essential action against the hypothermia being observed.

328 TABLET.

G. ZETLER CATALEP~CSTATE

AND

HYPOTHERMIAINMICECAUSEDBYTHECOMBINEDAPPLICA~ONOFPARAOXON AND PRALIDOXIME

Simultaneouslyinjected drugs* Experiment No.

Cataleptic state Cataleptic

S.C.

(mg/kg)

I II III IV V VI VII

Saline Saline Saline Paraoxon Paraoxon Paraoxon Paraoxon

(1) (1) (1) (1)

VIII

Paraoxon

(1)

IX

Paraoxon

(1)

X

Paraoxon

(1)

i.p.

(mg/kg)

Injected

Pralidoxime Pralidoxime Pralidoxime Pralidoxime Pralidoxime Pralidoxime Pralidoxime + Atropine Pralidoxime + Atropine Pralidoxime + Scopolamine Pralidoxime + Scopolamine

(100) (75) (50)

l/10 2110 2/10 919 14/14 8/8

‘\YF; (50) (75) (10) (75) (20)

Hypothermia

Compared with Exp. No.

MDT** P

“C

I II III

< OGOl
-0~18~0~181 +0.07+0+216 --0.03+0~12 4.8 *0.46 4.3 ho.25 -5.4 ho.58

V VII


V


13/15 2115

(1:; (75) (2)

9/10

-1.5

10.3t

-0.8

&0*167tt

-3*53&0.58§

3/15

-3.03&0.46§

(*)In the experiments Nr. VII-X pralidoxime and atropine or scopolamine were dissolved and injected together in the same volume of fluid. (**)Mean intra-individual difference of body temperature % i SE, in the experiments Nr. IV-X statistically different from zero (P= < 0.001). tP= < 0.05, for the difference from the result of experiment Nr. V. ttP= ~001, ditto. §P= > 0.4, ditto.

TABLE 2. ANTI-CATALEPTIC AND ANTI-HYPOTHERMIC ACTIONS IN MICE OF ANTICHOLINERGICS AND ANTIDEPRESSANTS, GIVEN 20 MIN BEFORE THE SIMULTANEOUS APPLICATION OF PARAOXON (1 mg/kg s.c.) AND PRALIDOXIME (75 mg/kg i.p.)

Pretreatment Experiment No. I

Drug Saline

II III IV

Atropine Atropine Atropine

V VI

Scopolamine Scopolamine

Cataleptic state mg/kg S.C.

Cataleptic Injected

Change in body temperature*

“C

P

-3.95&0.15

-

919

2.5 5 10

lO/lO 3/10 2110

< O*Ol
-1.83 kO.23 -1.05iO.26 -0.94Zto.39

8/10 l/9

< OGOl

-3.7410.25 -360&0*65

0.25 0.5

Imipramine Imipramine

20 40

7110 319

< 0+05

,4.1 -4.6

1x X

Desipramine Desipramine

10 20

7110 419

i 0.02

-2.63 LO.34 -3.61 ltO.37

Xl XII

Amitriptyline Amitriptyline

5 10

7110 4110

< 0.01

-3.96&0.34 -3.9 SO.37

VII VIII

*In all experiments the mean intra-individual different from zero.

P

difference in body temperature


AO.42 40.32 io.01

was statistically significantly

Cataleptic state and hypothermia

329

in mice

2. Catalepsy due to arecoline, pilocarpine and tremorine

As shown in Table 3, pilocarpine, arecoline and tremorine elicited catalepsy in mice pretreated with methylatropine; the anticholinergics and antidepressants were inactive in this respect. The cataleptic state was not so marked in these experiments as after paraoxon (Tables 1 and 2), and much lower doses of atropine and scopolamine were sufficient for antagonism. Scopolamine was about ten times more active than atropine. The catalepsy after arecoline was much less resistant against some antagonists, especially amitriptyline, than that after pilocarpine and tremorine. Thus desipramine was as active as imipramine in antagonizing the effects of arecoline, but in contrast to imipramine was inactive against pilocarpine and tremorine. The changes of body temperature during the experiments of Table 3 are shown in Table 4. The fall of body temperature was much greater after tremorine than after arecoline or pilocarpine although the doses of these three cholinergics were equi-active with respect to catalepsy. Table 4 reveals surprising differences between the anticholinergics. Atropine antagonized hypothermia by arecoline, pilocarpine and tremorine, whereas scopolamine was inactive against tremor-me although it even transformed arecoline- and pilocarpine-hypothermia into a weak hyperthermia. Atropine, on the other hand, in a dose inactive against catalepsy was still highly active against tremorine hypothermia. The antidepressants did not reduce hypothermia which was, in case of arecoline, enhanced by 20 mg/kg of amitriptyline. TABLET.

CATALEPTICSTATE*

INM~CECAUSEDBYARECOLINE,PILOCARPINEANDTREMORME,EACHCOMBINED

Second injection (i.p.) 20 min later

First injection(s.c.)

Saline Drug

mg/kg

Methylatropine

5

Atropine Atropine Atropine

1 2.5 5

Scopolamine

0.05

Scopolamine Scopolamine Scopolamine

0.1 0.25 0.5

4114 -

Arecoline 20 mg/kg 16120

Pilocarpine g mgkg 11/15

Tremorine 6 mglk g IO/l6

7110 o/10 c 2/10 a

6/10 l/l0 b 3115 a

s/10 l/lOa O/l0 b

-

7110

-

-

o/lo

6115 a l/l0 b o/10 c

S/IO l/IO b o/10 c

g/9 l/l0 a 4119 a

o/lo

Imipramine Imipramine Imipramine

5 10 20

2/10 o/10

5/10 3/lOa 3/lOa

12120 4115 a

4110 3115 a

Desipramine Desipramine Desipramine

5 IO 20

2/10 2/10

6/10 3110 a 3115 b

$5 11/20

6115 6115

Amitriptyline Amitriptyline Amitriptyline Amitriptyline Amitriptyline

1 2.5 1: 20

* Expressed as “cataleptic animals/injected a: P -x0.05 b: P < 0.01 c: P < 0XlO1

2ilo o/10 animals”,

7110 3/lOa 2110 a l/IO b o/10 c

6115 o/10 c

9/10 2115 a O/10 b

330

G. ZETLER

TABLE4. CHANGESIN

BODY

TEMPERATURE* DURINGTHE

First injection (s.c.)

Drug

mg/kg

EXPERIMENTS WHICH

ARE SUMMARIZED

IN

TABLE 3

Second injection (i.p.) 20 min later Saline “C

Arecoline 20 mg/kg “C

Pilocarpine 8 mg/kg “C

Tremorine 6 mg/kg “C

Methylatropine

5

--0.52f0.22*

-1.66&0*16

-1*22&0.22

Atropine Atropine Atropine

1 2.5 5

-0.84&0.12*

--0.13&0*22 a -0.13+0.28 a -0.82kO.42 a’

-1.6210.16 -1.27&0.18 -@20&0.13

Scopolamine Scopolamine Scopolamine Scopolamine

0.05 0.1 0.25 0.5

+044s*25

+0.06*0.11 a’ +O@t&O~13 a +044&0.24 b +0.31&0*13+b

+0.44&0.12+b +0.13*0.21 a +064&0.20+b

-4.4210.51 n -3.26+0.48n -3.75+0.31 n

-

-556ztO.32 n n b’

--@24+0*24 b --0.27+0.15 b -07610.20 b’

Imipramine

20

-0.34f0.12*

-2.02f0.21

n

-2.36&0.26

n

--4.40f0.36

n

Desipramine

20

+0.38&0*22

-1.1210.34

n’

-2.08 50.22 n

-3.6710.34

n

Amitriptyline Amitriptyline

10 20

-1.08&0.22* 4.92hO.48

-1.77-1-0.32 n’ +04*0.62 b

-1.92kO.25 -3.12rt0.35

-3.89+0.30 -2.891064

n n

n n

*Mean intra-individual difference of body temperature % + SR. P-values for statistical comparison with the methylatropine experiments: n= P> 0.05. a= P -c0.05, b= P < 0.01;an apostrophe indicates that the variances of the means to be compared were different and the ranking method was used. An asterisk means that the mean change in body temperature was statistically significant (this was checked and mentioned only for the experiments with saline and in cases of hyperthermia).

3. Catalepsy due to nicotine Nicotine, too, produced catalepsy (Table 5). The animals showed no signs of peripheral autonomic stimulation indicating that the dose of hexamethonium applied was sufficient for peripheral protection. The nicotine dose was too low to elicit clonic convulsions and, therefore, the nicotine catalepsy cannot be due to post-convulsive depression of the central nervous system. The nicotine catalepsy was antagonized by the same drugs and doses which were effective against the muscarinic stimulants of Table 3. Scopolamine was again about ten times more active than atropine, whereas desipramine was clearly of lower potency than imipramine. Nicotine catalepsy was not accompanied by hypothermia. As shown in Table 5 the mean changes of body temperature were only significantly altered after 10 and 20 mg/kg of desipramine and 5 mg/kg of amitriptyline. DISCUSSION

Central cholinergic stimulation is very probably the unitary mechanism of cataleptic action for the chemically dissimilar drugs arecoline, pilocarpine, tremorine, nicotine, and paraoxon, the latter acting as an inhibitor of acetylcholineesterase. Such a mechanism would also explain the marked anticataleptic activity of atropine and scopolamine as well as the difference in potency between the two drugs, since scopolamine is about 10 times more effective than atropine as a central anticholinergic drug. Thus, it seems justified to suggest that cataleptic akinesia can arise from cholinergic stimulation of the central nervous system. Indeed, FELDBERG and SHERWOOD (1954) have described cataleptic stupor in cats after intraventricular injections of acetylcholine, diisopropylfluorophosphate and

Cataleptic state and hypothermia in mice TABLE 5. CATALEPTIC STATE IN MICE CAUSED BY NICOTINE (7 mg/kgi.p.)20 METHONIUM (5 mg/kg i.p.) WAS GIVEN FOR PERIPHERAL

Pretreatment* Drug

Catalepticstate m&g S.C.

Cataleptic Injected

P

14120

Saline

331 min BEFORE NICOTINE,HEXAPROTECTION

Changein body temperaturet “C -006&0.21

2.5 5

7110 7115 2115 o/10

< 0.01
+1.4 +0.72 -0~38~0~18 +0.2 h-o.24 +0.15*0.09

Scopolamine Scopolamine

0.05 0.1

5110 l/10


-0.08 ho.22 -0.26*0*22

Imipramine Imipramine

2 5

7115 3115

< 0.01

-O-24*0*29 -0*39*0.34

Desipramine Desipramine Desipramine

5 10 20

6115 5/15 3115


-0.28~tO.31 -0.5450.25 -0.98f0.20

Amitriptyline Amitriptyline

2 5

7115 4115

< 0.05

-0.47f0.35 -1.13&0*23

Atropine Atropine Atropine A&opine

0.5 1

*Theseinjectionswere given 10min before nicotine. tMean intra-individualdifferencesof body temperatureX f sR.

eserine. Cataleptic actions of the other cholinergic drugs used here have not to our knowledge been described. The reduced motor activity or akinesia seen in mice and chicks after tremorine (EVERETTet al., 1956; EVERETT,1964; LEVYand MICHEL-BER,1964; BowMAN and OSUIDE, 1967; MORPURGO,1967) is a consequence of the cataleptic state. Acetylcholine possibly plays an essential role in the chain of cataleptogenic events since it accumulates in brain not only after paraoxon but also after tremorine (PEPEU, 1963; HOLMSTEDTand LUNDGREN,1966; BOWMANand OSUIDE, 1967) and it decreases after atropine and scopolamine (GIARMANand PEPEU, 1962, 1964; PEPEU, 1963; PAZZAGLI and PEPEU, 1965). Furthermore, arecoline leads in viva and in vitro to an increase of acetylcholine concentration in brain tissue, and this is prevented by atropine (HOLMSTEDT and LUNDGREN,1967). These findings do not exclude a direct influence of central cholinergics and anticholinergics on cholinergic receptors. The high anticataleptic potency of atropine and scopolamine suggests that the central cholinergic stimulation was muscarinic. This applies also to the cataleptic action of nicotine. This drug, consequently, is not completely lacking central muscarinic activity as e.g. CONNORet al. (1966) concluded from the results of nicotine injections into the caudate nucleus. The statement that nicotine has central muscarinic activity is, indeed, surprising but supported by a considerable body of indirect evidence of an acetylcholine mimicking or releasing action of nicotine in the central nervous system (KNAPP and DOMINO,1962; ARMITAGEet al., 1966, 1967; ARMITAGEand HALL, 1967). The finding that nicotine, in contrast to arecoline, does not increase the acetylcholine content of whole or homogenized brains (HOLMSTEDTand LUNDGREN,1967) is not contrary to this view unless it is confirmed

332

G. ZETLER

with selected brain areas. Even then, only the acetylcholine releasing but not the acetylcholine mimicking activity of nicotine could be refuted. The hypothermia caused by such chemically differing compounds as paraoxon, arecoline, pilocarpine, and tremorine is very probably the result of a central muscarinic stimulation for it appeared in peripherally protected animals (no salivation, lachrymation or defecation) and was antagonized by atropine. This view-as far as tremorine is concerned -is in agreement with that of EVERETT(1964), LOMAXand JENDEN(1966) and SPENCER (1966); it is confirmed by the finding that physostigmine lowers the body temperature of rats (MAICKEL et al., 1964). Thus, central cholinergic mechanisms play an important role for the maintenance of body temperature. The results summarized in Table 6 lead to the conclusion that catalepsy and hypothermia are independent effects of central cholinergic stimulation. Accordingly, catalepsy TABLE 6. INFLUENCEON CHOLINERGICHYPOlWERMIAOF .~NT~CHOLINERO~CS AND ANTIDEPRESSANTS, GIVEN IN FULLY ANTICATALEPTIC DOSES. THIS TABLE SUMMARIZESTHE DETAILSGIVEN IN THE FOREGOINGTABLES Cataleptic drugs Anticataleptic

drugs

Paraoxon

Atropine

Arecoline

Pilocarpine

Tremorine

+

-t

-!

Scopolamine

-

+ hyper

+hyper

-

Imipramine

-

-

Amitriptyline

-

+ Antagonism - no Antagonism

+

-

-hypo

-

-

hyper : Hyperthermia. hypo: Hypothermia increased.

is not a consequence of the decrease in body temperature, nor is the hypothermia caused by akinesia: in experiment No. VII of Table 1 and No. II of Table 2, furthermore, after the combination of 1 mg/kg of atropine with arecoline and tremorine (cf. Tables 3 and 4) and in other experiments, hypothermia was greatly reduced or even changed into hyperthermia (scopolamine plus arecoline or pilocarpine) although catalepsy was present. It is not clear why the nicotine catalepsy was not accompanied by hypothermia. It is unlikely to be caused by a simultaneous stimulation by nicotine of compensating noncholinergic centres or mechanisms, since there was no hyperthermia after anticataleptic doses of atropine or scopolamine. Nevertheless, the results achieved with nicotine support the conclusion that catalepsy and hypothermia are independent phenomena. The anti-hypothermic action of scopolamine was, as Table 6 shows, considerably different from that of atropine, at least in the anticataleptic dose range. This clear-cut finding was surprising since from all available results of animal experimentation scopolamine is a central anticholinergic drug at least 10 times more active than atropine. In our experiments, the antidepressants were inactive against cholinergic hypothermia, and for tremorine this is in disagreement with the findings of SPENCER (1965, 1966) and MORPURGO (1967). These authors, however, not only applied higher doses of drugs including tremorine in most experiments but worked with animals unprotected against the strong peripheral actions of cholinergics. It can be assumed that in these animals sweating and strong salivation (moist chin, neck and breast) lead to greater heat losses which were diminished or

Cataleptic state and hypothermia

in mice

333

abolished simply by peripheral anticholinergic action of the antidepressants. This explanation applies also to the unexpected lack of effect of scopolamine against tremorine hypothermia. On the other hand, our observation that the antidepressants in question do not antagonize hypothermia is in accord with the finding of HALLIWELLet al. (1964) that imipramine, desipramine, and amitriptyline have no essential central anticholinergic activity and do not, in contrast with atropine, antagonize the arecoline-induced block of conditioned reflex. The failure of imipramine and amitriptyline to antagonize hypothermia even in anticataleptic doses, and the very low anti-hypothermic potency of desipramine, indicate a very weak central anticholinergic activity. The results of these and earlier experiments (ZETLER, 1963) that desipramine has weaker anticataleptic potency than imipramine correspond to the observation that demethylation of imipramine and amitriptyline reduces peripheral anticholinergic and central, i.e. EEG arousal inhibiting activity (BRIMBLECOMBE and GREEN, 1967). Since, however, demethylation of imipramine does not diminish but rather enhances the antidepressant potency (BRODIE et al., 1961), the antagonism against cholinergic catalepsy does not reflect antidepressant activity. Acknowledgemenfs-I am very much indebted to Mrs Ruth &heel and Miss Christel Wendorff for their careful technical assistance.

REFERENCES evidence relating to the mode of action of nicotine in thecentral nervous system. Nature, Land. 214: 977-979. ARMITAGE,A. K., HALL, G. H., MILTON, A. S. and MORRISON,C. F. (1967). Effects of nicotine injected into and perfused through the cerebra1 ventricles of the cat. Arm. N. Y. Acad. Sci. 142: 27-39. ARMITAGE,A. K., MILTON, A. S. and MORRISON,C. F. (1966). Effects of nicotine and some nicotine-like compounds injected into the cerebral ventricles of the cat. Er. J. Pharmacol. 27: 33-45. BASTIAN,J. W. (1961). Classification of CNS drugs by a mouse screening battery. A&s. int. Pharmacodyn. 133: 347-364. BENESOV&O., BOHDANECK~,Z. and GROFOV~~,J. (1964). Electrophysiological analysis of the neuroleptic and antidepressant actions of psychotropic drugs in rabbits. Int. J. Neuropharmacol. 3: 479-488. BOWMAN,W. C. and OSUIDE, G. (1967). Effects of tremorine and harmine in the chick. Europ. J. Pharmacol. 1: 71-80. BRIMBLECOMBE, R. W. and GREEN, D. M. (1967). Central effects of imipramine-like anti-depressants in relation to their peripheral anticholinergic activity. Int. J. Neuropharmacol. 6: 133-142. BRODIE,B., DICK, P., KIELHOLZ,W., POELDINGER,W. and THEOBALD,W. (1961). Preliminary pharmacological and clinical results with desmethylimipramine (DMI) G 35020, a metabolite of imipramine. Psychopharmacologia 2 : 467-474. CONNOR, J. D., ROSSI, G. V. and BAKER, W. W. (1966). Analysis of the tremor induced by injection of cholinergic agents into the caudate nucleus. Inr. J. NeuropharmacoL 5: 207-216. COURVOISIER,S., DUCROT, R. and JULOU, L. (1957). Nouveaux aspects exp&imentaux de I’activitC centrale des d&ids de la phknothiazine. In Psychotropic Drugs, (S. GARA~INI and V. GHETTI, Editors), Elsevier, Amsterdam. pp. 373-391. EDERY,H. and SCHA-~ZBERG-PORATH, G. (1959). Prophylactic and therapeutic effects of pyridine-2-aldoxime methoiodide and diacetyl monoxime against poisoning by organophosphorous compounds. Archs int. Pharmacodyn. 121: 104-109. ERDMANN,W. D. (1965). Vergleichende Untersuchungen iiber das Penetrationsvermagen einiger esterasereaktivierender Oxime in das zentrale Nervensystem. Arzneimiftel-Forsch. 15: 135-139. ESSMAN, W. B. and SUDAK, F. N. (1963). Effect of hypothermia on the establishment of a conditioned avoidance response in mice. J. camp. physiol. Psychol. 56: 366-369. EVERETT,G. M. (1964). Pharmacological studies on tremorine. Proc. 2nd inter. Pharmacol. Meet. 2: 69-74. EVERETT,G. M., BLOCKUS,L. E. and SHEPPERD,I. M. (1956). Tremor induced by Tremorine and its antagonism by anti-Parkinson drugs. Science 124: 79. FELDBERG,W. and SHERWOOD,S. L. (1954). Behaviour of cats after intraventricular injections of eserine and DFP. J. Physiol. (Land.) 125: 488-500. ARMITAGE,A. K. and HALL, G. H. (1967). Further

G. ZETLER

334

FLEISHER,J. H., HARRIS, L. W. and MURTHA, E. F. (1967). Reactivation by pyridinium aldoxime methochloride (PAM) of inhibited cholinesterase activity in dogs after poisoning with pinacolyl methylphosphonofluoridate (Soman). J. Phurmacol. exp. Ther. 156: 345-351. GIARMAN, N. J. and PEPEU, G. (1962). Drug-induced changes in brain acetylcholine. Br. J. Pharnmcol. 19: 226-234. GIARMAN,N. J. and PEPEU, G. (1964). The influence of centrally acting cholinolytic drugs on brain acetylcholine levels. Br. J. Pharmacol. 23: 123-130. GINZEL, K. H. (1967). Introduction to the effects of nicotine on the central nervous system. Ann. N. Y. Acnd. Sci. 142: 101-120. HALLIWELL,G., QUINTON, R. M. and WILLIAMS,F. E. (1964). A comparison of imipramine, chlorpromazine and related drugs in various tests involving autonomic functions and antagonisms of reserpine. Br. J. Pharmacol.

23: 330-350.

HERZ, A. (1965). Central cholinolytic activity and antidepressive effect, In Neuropsychopharmacology, Vol. 4 (D. BENTEand P. B. BRADLEY,Editors). Elsevier. Amsterdam. DD. 402404. HERZ, A., HOLZHKUSER,H. und TESCHEMACHER,‘H.(1966): Zentrale und periphere Wirkungen von Cholinomimetica und ihre Abhlngigkeit von der Lipoidloslichkeit. Naunyn-Schmiedeberg’s Archs esp. Path. Pharmak.

253: 280-297.

HOBBIGER,F. (1957). Protection against the lethal effects of organophosphates by pyridine-2-aldoxime methoiodide. Br. .I. Pharmacol. 12: 438446. HOBBIGER,F. and SADLER,P. W. (1959). Protection against lethal organophosphate poisoning by quaternary pyridine aldoximes. Br. J. Pharmacol. 14: 192-201. HOLMSTEDT, B. and LUNDGREN,G. (1966). Tremorgenic agents and brain acetylcholine. In Mechanisms of Release of Biogenic Amines, U. S. VON EULER, S. ROSELLand B. UVNV;~S,Editors), Pergamon Press, Oxford. pp. 439-468. HOLMSTEDT,B. and LUNDGREN, G. (1967). Arecoline, nicotine, and related compounds, tremorgenic activity and effect upon brain acetylcholine. Ann. N. Y. Acad. Sci. 142: 126-142. KEWITZ, H. and NACHMANSOHN, D. (1957). A specific antidote against lethal alkyl phosphate intoxication. IV. Effects in brain. Archs Biochem. 66: 271-283. KNAPP, D. E. and DOMINO, E. F. (1962). Action of nicotine on the ascending reticular activating system. Int. J. Neuropharmacol. 1: 333-351. LAURENCE,D. R. and STACEY.R. S. (1953). Mechanism of the prevention of nicotine convulsions by hexamethonium and by adrenaline blocking agents. Br. J. Pharmacol. 8: 62-65. LESLIE,G. B. and MAXWELL,D. R. (1964). Some pharmacological properties of thioproperazine and their modification by anti-parkinsonian drugs. Br. J. Pharmacol. 22: 301-317. LESSIN, A. W. and PARK&, M. W. (1957): The relation between sedation and body temperature in the mouse. Br. J. Pharmacol. 12: 245-250. LEVY, J. and MICHEL-BER,E. (1964). De l’antagonisme vis-h-vis de diffkrents effects de la tremorine chez la souris. Proc. 2nd. Int. Pharmacol. Meet. 2: 109-l 14. LOEW, D. and TAESCHLER,M. (1965). Central anticholinergic properties of antidepressants. In Nertropsychopharmacology, Vol. 4 (D. BENTEand P. B. BRADLEY,Editors), Elsevier, Amsterdam. pp. 404-407. LOMAX, P. and JENDEN, D. J. (1966). Hypothermia following systematic and intracerebral injection of oxotremorine in the rat. Int. J. Neuropharmacol. 5: 353-359. MAICKEL,R. P., STERN,D. N. and BRODIE,B. B. (1964). The role of autonomic nervous function in mammalian thermoregulation. Proc. 2nd. Int. Pharmacol. Meet. 2: 225-237. MILLER NIELSEN,I., NYMARK,M., Houcs, W. and PEDERSEN,V. (1966). The pharmacological properties of Melitracen (N 7001) and Litracen (N 7049). Arzneimittel-Forsch. 16: 135-140. MORPURGO, C. (1962). Effects of antiparkinson drugs on a phenothiazine-induced catatonic reaction. Archs int. Pharmacodyn.

137: 84-90.

MORPURGO,C. (1965). Antiparkinson drugs and neuroleptics. Prog. Bruin Res. 16: 121-134. MORPURGO, C. (1967). Interaction of imipramine and desmethylimipramine with tremorine and oxotremorine in mice. Life Sci. 6: 721-731. MORPURGO, C. and THEOBALD,W. (1964). Influence of antiparkinson drugs and amphetamine on some pharmacological effects of phenothiazine derivatives used as neuroleptics. Psychopharmaco/ogin 6: 178-191. PATON,W. D. M. and ZAIMIS,E. J. (1952). The methonium compounds. Pharmacol. Rev. 4: 219-253. PAZZAGLI,A. and PEPEU, G. (1965). Amnesic properties of scopolamine and brain acetylcholine in the rat. Int. J. Neuropharmacol.

4: 291-299.

PEPEU, G. (1963). Effect of “tremorine” and some anti-Parkinson’s disease drugs on acetylcholine in the rat’s brain. Nature, Lond. 200: 895. PFEIFFER,C. C. and JENNEY,E. H. (1957). The inhibition of conditioned response and the counteraction of schizophrenia by muscarinic stimulation of the brain. Ann. N. Y. Acod. Sci. 66: 753-764.

Cataleptic state and hypothermta

m mice

335

RIBBENTROP,A. und SCHAUMANN,W. (1965). Zentrale anticholinerge Wirksamkeit und Spezifitat einiger Derivate des Granatans. Arzneimiftel-Forsch. 15:857-862. RUTLAND,J. P. (1958). The effect of some oximes in sarin poisoning. Br. .7. Pharmacol. 13: 399-403. SCHAUMANN,W. und KURBJUWEIT,H. G. (1961). Beeinflussung verschiedener Wirkungen von Thiopropazat durch ein zentrales Stimulans. Arzneimitfel-Forsch. 11:343-350. SCHAUMANN,W. und RIBBENTROP,A. (1966). Interferenz der zentrallen anticholinergen Wirkung bei der tierexperimentellen Prtifung potentieller Antidepressiva. Arzneimittei-Forsch. 16: 645-649. SPENCER, P. S. J. (1965). Activity of centrally acting and other drugs against tremor and hypothermia induced in mice by tremorine. Br. J. Pharmacol. 25: 442-455. SPENCER, P. S. J. (1966). The antagonism of oxotremorine effects in the mouse by thymoleptics. Lifi Sci. 5: 1015-1023.

SUDAK, F. N. and ESSMAN,W. B. (1962). Maze acquisition

and retention in hypothermic mice. J. oppl. Physiol. 17: 747-750. SULSER, F., BICKEL, M. H. and BRODIE,B. B. (1964). The action of desmethylimipramine in counteracting sedation and cholinergic effects ofreserpine-like drugs. J. PharmacoL exp. Thu. 144:321-330.

TAESCHLER,M., WEIDMANN,H. und CERLETTI,A. (1962). Zur Pharmakologie von Ponalid, einem neuen zentralen Anticholinergicum. Schweiz. med. Wschr. 92: 1542-1545. THEOBALD,W., BUCH, O., KUNZ, H. A. und MORPURGO,C. (1966). Zur Pharmakologie der Metaboliten des Imipramins. Med. Pharmacol. exp. 15: 187-197. THEOBALD,W., BUCH, O., KUNZ, H. A., MORPURGO,C. STENGER,E. G. und WILHELMI,G. (1964). Vergleichende pharmakologische Untersuchungen mit Tofranil, Pertofran und Insidon. Archs inf. Pharmacodyn.

148: 560-596.

TOMAN,J. E. P. (1963) Some aspects of central nervous pharmacology. Ann. Rev. Pharmacol. 3: 153-184. VERNIER,V. G. and UNNA, K. R. (1956). The experimental evaluation of antiparkinson compounds. Alan. N. Y. Acad. Sci. 64: 690-704. ZETLER, G. (1960). Pharmakologische Eigenschaften antidepressiv wirkender Pharmaka. Dtsch. med. Wschr. 85: 2276 -228 1. ZETLER, G. (1963). Die antikataleptische Wirksamkeit einiger Antidepressiva (Thymoleptica). Arzneimittel-Forsch.

13: 103-109.

ZETLER,G., MAHLERK. und DANIEL, F. (1960). Versuche zu einer pharmakologischen Differenzierung kataleptischer Wirkungen. Naunyn-Schmiedeberg’s Archs exp. Path. Phcrrnmk. 238: 486-501. ZETLER,G. und Mooo, E. (1958). Die Bulbocapnin-Katatonie, ihre Synergisten und Antagonisten. NaunynSchmiedeberg’s Archs exp. P&h. Pharmak. 232: 442-458.