Potentiation by neuroleptic agents of the inhibitory action of intraperitoneally administered GABA on the locomotor activity of mice

Pharmacology Biochemistry & Behavior, Vol. 8, pp. 651-654. Printed in the U.S.A.

Potentiation by Neuroleptic Agents of the Inhibitory Action of Intraperitoneally Administered GABA on the Locomotor Activity of Mice BRATATI BISWAS AND ARVID CARLSSON

Department o f Pharmacology, Universi~ o f Gdteborg, G6teborg, Sweden (Received 12 December 1977)

BISWAS, B. AND A. CARLSSON. Potentiation by neuroleptic agents of the inhibitory action of intraperitoneally administered GABA on the locomotor activity of mice. PHARMAC. BIOCHEM. BEHAV. 8(6) 651-654, 1978. - The ability of several neuroleptics to potentiate the inhibitory action of IP administered GABA on the motor activity of mice has been investigated. Haloperidol, chlorpromazine, thioridazine, and clozapine, but not the apparently selective dopamine receptor-blocking agent spiperone, were found to possess such activity. Phenoxybenzamine also proved active in potentiating GABA. Thus blockade of dopamine receptors as well as a-adrenergic receptors may be responsible for neuroleptic-induced potentiation of GABA actions. Neuroleptics

GA BA

Locomotor activity

IN PREVIOUS communications we have presented evidence that systemically administered GABA is capable of influencing central monoaminergic mechanisms and of exerting a central depressant action [2,3]. The pattern of activity was similar to that observed after intracerebroventricular administration of GABA [4], thus supporting the hypothesis that G ABA is capable of reaching at least certain central neurons from the blood stream. In otherwise untreated animals the IP dose of the GABA required for inhibiting motor activity to a significant degree was rather high, i.e., 2000 mg/kg. However, a considerable increase in the sensitivity to GABA was brought about by pretreatment with ethanol or haloperidol, where IP GABA proved active in doses down to 100 mg/kg after such pretreatment. In agreement with these observations Kh/iri~inen [6] reported that amino-oxyacetic acid, an inhibitor of GABA transaminase, and baclophen, a GABA derivative, are capable of potentating the cataleptic action of haloperidol. In the present communication the ability of haloperidol and several other neuroleptic agents to potentiate the action of 1P administered GA BA is further investigated. METH o I) Female mice weighing about 20 g of the NMRI strain were used. The following drugs were administered: Haloperidol (Haldol ®, AB Leo*, Helsingborg, Sweden), spiperone (Janssen*, Beerse, Belgium), ciozapine (Wander*,

Bern), chiorpromazine HC1 (Hibernal®, AB Leo*, Helsingborg, Sweden), thioridazine HCI (Mallorol ®, Sandoz*, Basle, Switzerland), phenoxybenzamine HCI (AB Leo*, Helsingborg, Sweden) and gamma-aminobutyric acid (GABA, Sigma). Locomotor activity was measured using the "M/P 40 Fc Electronic Motility Meter" (Motron Products, Stockholm) [1]. Every tenth interruption of the photocell beam was counted. The animals in groups of three were placed in each activity box and cumulative counts for 20 min were recorded. Thioridazine (0.5 mg/kg), clozapine ( i . 0 mg/kg) and chlorpromazine (0.3 mg/kg) were injected alone or in combination with GABA (100 mg/kg). Spiperone was injected at different doses (0.01 to 0.15 mg/kg) in combination with the same dose of GABA. Different doses of haloperidol (0.025 to 0.15 mg/kg) were injected, either alone or in combination with different intraperitoneal doses of GABA (5 to 250 mg/kg). All neuroleptics were given before the injection of GABA or corresponding saline. (The exact time of injection has been mentioned in the RESULT section.) Recording locomotor activity was started about 1 min after the injection of GABA. Phenoxybenzamine (0.5 mg/kg and 0.75 mg/kg) was given 1 hr prior to GABA injection.

Statistics Statistical calculations were done by one-way analysis of variance followed by Student's t test.

C o p y r i g h t © 1978 A N K H O I n t e r n a t i o n a l Inc.--0091-3057/78/0806-0651500.60/0

652

BISWAS AND CARLSSON

300

._c E

Q

u)

?,

200

o

%

._~ 4f~

8 ~ 100 o ._1

o

6

"

560

tSo

is Dose of GABA (rng//kg)

FIG. I. Effect of various doses of GABA (given IP 1 min before recording) on the locomotor activity of mice, pretreated with haloperidol (O. 15 mg/kg IP, 20 rain before recording

RESULTS The dose-response curve of IP administered GABA in mice pretreated with a fixed dose of haloperidol (0.15 mg/kg) is shown in Fig. I. Doses down to 5 mg/kg proved active in inhibiting motility. A certain further inhibition was observed after higher doses of IP GABA. If the pretreatment dose of haloperidol was reduced from 0.15 to 0.05 mg/kg, a dose still active per se, GABA, 100 mg/kg IP, produced but a slight, statistically not significant decrease in motility (Table l ). Haloperidol appears to be a rather selective dopaminereceptor blocking agent. It appears to be capable of blocking also a-adrenergic "receptors although larger doses are required [5]. Spiperone appears to be an even more selective dopamine-receptor blocking agent. However, this

agent appeared to be unable to potentiate the action of IP GABA (Table 2). A number of neuroleptics with lower selectivity as regards blockade of dopamine receptors, i.e., chlorpromazine, thioridazine and clozapine, were also investigated. When given in doses which per se were inactive (thioridazine and chlorpromazine) or moderately active (clozapine), they were all found to potentiate the action of IP GABA (Table 3). Since the neuroleptics studied in Table 3 appear to block not only dopamine receptors but also a-adrenergic receptors [5], the effect of phenoxybenzamine, a potent aodrenergic receptor-blocking agent, was also investigated. When given in an IP dose of 0.75 but not 0.5 mg/kg, it proved active in potentiating the action of IP GABA (Table 4). A

TABLE 1 EFFECT OF HALOPERIDOL AND GABA ON THE LOCOMOTOR ACTIVITY OF MICE

Locomotor Activity (counts/20 rain) Treatment

Dose (mg/kg)

Saline Haloperidol

Drug + Saline (a)

Drug + GABA (b)

p (a) vs. (b)

461 + 15 (16)

444 + 41

(5)

>0.05

0.05

331 + 31"

(8)

285 +- 9 (7)

>0.05

0.15

242 ± 22

(9)

169 + 15

<0.05

(6)

Variance within groups = 4168. Shown are the means -+ SEM. Figures in parentheses indicate number of experimental groups, each comprising three animals. *p<0.001 vs. saline. Haloperidol was given 20 min and GABA (100 mg/kg IP) 1 rain before measuring the locomotor activity.

I N T E R A C T I O N BETWEEN N E U R O L E P T I C S AND G A B A

653

TABLE 2 EFFECT OF VARIOUS DOSES OF SPIPERONE ALONE OR IN COMBINATION WITH GABA ON THE LOCOMOTOR ACTIVITY OF MICE

Locomotor Activity (counts/20 min) Dose

Treatment

(mg/kg)

Drug + Saline

Drug + GABA

461" ± 15 (16)

444 ± 41 (5)

0.01

362

327 ± 33 (5)

0.02 0.03

Saline Spiperone

± 16

(7)

320

± 29

(5)

322 ± 23 (5)

387

± 34

(6)

322 + 40 (6)

0.06

373

± 30

(4)

357 ± 42 (5)

0.10

244

± 18

(4)

245 ± 17 (4)

0.15

151

± 10

(4)

170 ± 23 (4)

Variance within groups = 4079. Shown are the means ± SEM. Figures in parentheses indicate number of experimental groups, each comprising three animals. *Differs from all spiperone-treated groups (p<0.005). Spiperone-treated groups vs. spiperone + GABA is always p>0.05. Spiperone was given 20 min and GABA (100 mg/kg IP) 1 min before measuring the locomotor activity. TABLE 3 EFFECT OF DIFFERENT NEUROLEPTICS ALONE OR IN COMBINATION WITH GABA ON THE LOCOMOTOR ACTIVITY OF MICE

Locomotor Activity (counts/20 rain) Treatment

Dose (mg/kg)

Drug + Saline (a)

Drug + GABA (b)

p (a) vs. (b)

Saline

-

461

+ 15 (16)

444 ± 41 (5)

>0.05

Thioridazine

0.5

464

-+ 38

(8)

313 -+ 21 (9)

<0.001

Clozapine

1.0

340* + 19

(8)

254 -+ 14 (5)

<0.05

Chiorpromazine

0.3

440

(6)

327 ± 17 (6)

<0.01

± 20

Variance within groups = 4564. Shown are the means -+ SEM. Figures in parentheses indicate number of experimental groups, each comprising three animals. *p<0.001 vs. saline. Thioridazine and clozapine were given 20 rain and chlorpromazine 1 rain before GABA. Locomotor activity was recorded 1 min after GABA (100 mg/kg, IP) injection.

c o m b i n a t i o n o f p h e n o x y b e n z a m i n e , 0.75 mg/kg, with s p i p e r o n e 0.06 mg/kg, a p p e a r e d n o m o r e p o t e n t t h a n p h e n o x y b e n z a m i n e alone in p o t e n t i a t i n g the a c t i o n o f IP GABA. I)iSCUSSION The p r e s e n t investigation has s h o w n t h a t a n u m b e r o f n e u r o l e p t i c agents are capable o f p o t e n t i a t i n g t h e inh i b i t o r y action o f IP a d m i n i s t e r e d G A B A o n t h e m o t i l i t y o f mice. H o w e v e r , s p i p e r o n e , an agent s u p p o s e d t o be highly selective in b l o c k i n g d o p a m i n e r e c e p t o r s , p r o v e d inactive in

this regard. On the o t h e r h a n d p h e n o x y b e n z a m i n e , a selective a - a d r e n e r g i c r e c e p t o r - b l o c k i n g agent, proved active. The q u e s t i o n m a y t h u s be raised w h e t h e r t h e a - a d r e n e r g i c r e c e p t o r - b l o c k i n g activity, w h i c h m a n y n e u r o leptics have in c o m m o n , a l t h o u g h this activity is generally less p r o n o u n c e d t h a n t h e d o p a m i n e r e c e p t o r - b l o c k i n g a c t i o n , m i g h t be r e s p o n s i b l e for p o t e n t i a t i o n o f GABA. It s h o u l d be recalled t h a t G A B A appears to s t i m u l a t e noradrenergic n e u r o n s [ 2 ] . It does n o t seem u n r e a s o n a b l e t o assume t h a t this s t i m u l a t i o n serves t o c o u n t e r a c t t h e inh i b i t o r y a c t i o n o f G A B A o n l o c o m o t i o n . The p r e s e n t data

BISWAS A N D C A R L S S O N

654 TABLE 4

EFFECT OF SPIPERONE, GABA AND PHENOXYBENZAMINE (PBZ) ON THE LOCOMOTOR ACTIVITY OF MICE

Locomotor Activity (counts/20 min) Treatment

Dose (mg/kg)

Drug + Saline (a)

Drug + GABA (b)

p (a) vs. (b)

Saline

-

444 -+ 41 (5)

>0.05

PBZ

0.5

390* ± 38

(6)

370 ± 11 (6)

>0.05

0.75

416

± 32

(6)

261 ± 20 (6)

<0.001

Spiperone

0.06

436

± 14

(5)

385 ± 21 (5)

>0.05

PBZ

0.75

+

+

433

± 33

(6)

294 ± 39 (6)

<0.001

Spiperone

0.06

461

± 15 (16)

Variance within groups = 4723. Shown are the means ± SEM. Figures in parentheses indicate number of experimental groups, each comprising three animals. *p<0.05 vs. saline. PBZ was given 60 rain and spiperone 1 min before GABA. Locomotor activity was measured 1 min after GABA (100 mg/kg IP) injection. do n o t c o n t r a d i c t this possibility, even t h o u g h s o m e o t h e r as y e t u n i d e n t i f i e d a c t i o n o f t h e n e u r o l e p t i c s i n v e s t i g a t e d m a y b e r e s p o n s i b l e f o r t h e i r ability t o p o t e n t i a t e s y s t e m i c a l l y a d m i n i s t e r e d G A B A . Moreover, it m a y be m e n t i o n e d in this c o n n e c t i o n t h a t d i f f e r e n t n e u r o l e p t i c s have b e e n claimed to affect b r a i n G A B A s y s t e m s d i f f e r e n t i a l l y [ 7 ] . A n a l t e r n a t i v e i n t e r p r e t a t i o n of t h e p r e s e n t o b s e r v a t i o n is t h a t n e u r o l e p t i c s in general are c a p a b l e o f p o t e n t i a t i n g IP G A B A b y m e a n s o f t h e i r d o p a m i n e r e c e p t o r - b l o c k i n g p r o p e r t i e s , t o w h i c h aadrenergic blockade may contribute. The exceptional b e h a v i o u r o f s p i p e r o n e w o u l d t h e n be d u e t o s o m e u n i d e n t i f i e d p r o p e r t y o f this agent, w h i c h w o u l d serve t o neutralize the GABA potentiation induced by dopaminereceptor blockade. In a n y e v e n t t h e o b s e r v a t i o n s m a d e in this i n v e s t i g a t i o n e m p h a s i z e t h e h e t e r o g e n e i t y o f t h e n e u r o l e p t i c drugs, w h o s e profile o f activity is p r o b a b l y d e t e r m i n e d b y several sites o f a c t i o n , in a d d i t i o n to b l o c k a d e of d o p a m i n e r e c e p t o r s . This h e t e r o g e n e i t y m u s t be k e p t in m i n d in f u t u r e i n v e s t i g a t i o n s on t h e i n t e r a c t i o n b e t w e e n n e u r o leptics a n d G A B A - e r g i c drugs.

In this discussion t h e a c t i o n of G A B A has b e e n s t a t e d t o b e p o t e n t i a t e d b y n e u r o l e p t i c drugs. T h e q u e s t i o n m a y be raised w h e t h e r it w o u l d n o t be p r e f e r a b l e t o s t a t e t h a t the a c t i o n o f n e u r o l e p t i c s is p o t e n t i a t e d b y G A B A . Since b o t h agents p e r se, w h e n given in s u f f i c i e n t l y large doses, have a n i n h i b i t o r y a c t i o n o n m o t i l i t y [3] we feel t h a t b o t h ways of s t a t i n g t h e r e l a t i o n s h i p are a c c e p t a b l e a n d t h a t t h e q u e s t i o n , as t o w h i c h way is p r e f e r a b l e , is largely academic. Very large i n t r a p e r i t o n e a l doses o f G A B A (25 m m o l e s / k g ) given in h y p e r o s m o t i c s o l u t i o n , have b e e n s h o w n to cause d e h y d r a t i o n of the b r a i n a n d to p r o t e c t against c o n v u l s i o n s [ 8 ] . The dosage of G A B A used in o u r s t u d y are a b o u t t w o orders of m a g n i t u d e lower, a n d t h u s d e h y d r a t i o n of t h e b r a i n is p r o b a b l y n o t an i m p o r t a n t f a c t o r for t h e activity described in t h e p r e s e n t paper. ACKNOWLEDGEMENTS This study was supported by grants from the Swedish Medical Research Council (Nos. 00155 and 4698). B.B. was supported by the Swedish lnstitute's Guest Scholarship. The skillful technical assistance of Mrs. Birgitta Holmgren and Miss Barbro J6rblad is gratefully acknowledged.

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