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.