Histological and molecular biochemistry

Inhibition and potentiation of apomorphine-induced hypermotility in rats by neuroleptics

The effect of apomorphine (ap) was investigated in rats kept in a familiar cage; 0.25-5 mg/kg s.c. produced a short-lasting, abnormal hypermotility consisting mainly of locomotion and sniffing without grooming. Ap was administered to rate pretreated s.c. with various drugs. Ap hypermotility was antagonized by 12 neuroleptics from different chemical groups. The ap inhibitory effect of 5 neuroleptics was decreased when the interval between pretreatment and ap administration was increased from 0.5 to 4 hr. Clozapine was the only neuroleptic showing no inhibition but potentiation at 4 hr. Mepazine, a phenothiazine lacking antipsychotic effects, as well as the NA receptor blockers aceperone and phenoxybenzamine, did not inhibit ap hypermotility. Ap was also given 24 hr after haloperidol and clozapine. At this time both neuroleptics showed ap potentiation. The ap inhibition and potentiation after a single administration of the neuroleptics is presumable due to selective blockade and subsequent supersensitivity of some DA receptors.

Inhibition of 4,alpha-dimethyl-m-tyramine (H 77/77)-induced hypermotility in rats by single and repeated administration of chloropromazine, haloperidol, clozapine and thioridazine

The effect of H 77/77 (5 mg/kg s.c.) on motility of rats kept in a familiar cage was investigated. H 77/77 produced hypermotility, which was reduced by oral pretreatment with chlorpromazine, haloperidol, clozapine and thioridazine. The 4 neuroleptics were administered acutely and for a 14 day period. H 77/77 was given 30 min after the single or last dose of neuroleptc (chronic treatment) condition. After both single and repeated administration the neuroleptics showed H 77/77-antagonism in doses ranging from 0.1-2.0 mg/kg. The effect on H 77/77 activity did not change significantly after repeated treatment. Clozapine and thioridazine, which clinically produce only minor extrapyramidal side effects, exert a weak effect or none at all in tests commonly used for neuroleptic activity. These 2 neuroleptics were potent H 77/77-antagonists. Inhibition of H 77/77-hypermotility may possibly be used as a test for neuroleptics.