EFFECT OF COCAINE ON SEXUAL-BEHAVIOR IN MALE STUMPTAIL MACAQUES (MACACA ARCTOIDES)

The effect of cocaine (0.01-1.0 mg/kg) on sexual behaviour was studied in four male stumptail macaques (Macaca arctoides). Following drug-sa line control administration, the behaviour of the male monkey with a f emale was observed for 30 min in two different behavioural conditions; in one of the conditions the baseline sexual activity was low, and in the other it was high (partial or complete separation of the male and the female between the sessions, respectively). The reversal of the c ocaine-induced effects was attempted by haloperidol (0.003-0.01 mg/kg) , a dopamine-2-receptor antagonist. Cocaine (0.1-1.0 mg/kg) produced a highly significant dose-dependent suppression in the number of ejacul ations. The cocaine-induced suppression of ejaculatory behaviour was c ompletely reversed by haloperidol. Haloperidol at the dose range used did not in itself influence ejaculatory behaviour. The effect of cocai ne on grooming, nonejaculatory mounting, aggression, or perineal inves tigations did not reach statistical significance. The possibility that cocaine at very low doses (0.01-0.1 mg/kg) might increase sexual acti vity was excluded in the behavioural condition with a low basal sexual activity. The results indicate that cocaine dose-dependently suppress es ejaculatory behaviour as a result of dopamine-2-receptor-mediated m echanisms. The cocaine-induced suppression of ejaculatory behaviour mi ght be explained by the strong rewarding effect of cocaine alone.