Antiapomorphine and locomotor effects of neuroleptics in rhesus monkeys.

Intramuscular injections of apomorphine (1 mg/kg) cause marked behavioral effects in rhesus monkeys including hyperactivity, repetitive stereotyped movements, chewing, tongue movements, licking, biting and vocalization. These effects occur within minutes of the injection and last 90-100 min. The antiapomorphine and locomotor depressant activity of chlorpromazine, haloperidol, MD 790501, sultopride and thioridazine, injected IM 1 hr before apomorphine, were assessed using a standardized rating procedure. All compounds antagonized the effects of apomorphine but differed in terms of potency and their relative effects on locomotor activity. The experimental compound MD 790501, a new benzamide derivative, was not only the most potent compound tested but, compared with its antagonism of apomorphine, caused the least marked depression of locomotor activity.