Dopamine and sexual behavior in the male rat: a reevaluation.

In castrated male rats treated with a low dose of testosterone propionate (0.40 mg/kg per week), the dopamine agonists amphetamine and amfonelic acid reduced mount latency without affecting other aspects of sexual behavior. Apomorphine, in doses between 0.05 and 0.15 mg/kg, and 1-DOPA 5-45 mg/kg + carbidopa 50 mg/kg, lacked effect on sexual behavior. Both amphetamine and amfonelic acid increased locomotor activity in a dose-dependent manner. Apomorphine, in the lowest dose, produced a reduction whereas the higher doses of this drug as well as all doses of 1-DOPA lacked effect on this behavior. In castrated animals implanted with a testosterone-filled Silastic capsule, showing a level of sexual activity indistinguishable from that of intact animals, amphetamine and amfonelic acid did not affect sexual behavior. The dopamine receptor antagonists haloperidol and cis(Z)-flupentixol reduced sexual behavior, whereas pimozide was without effect in the dose range used. The doses of haloperidol and flupentixol that were required to reduce sexual activity were such that they also affected motor execution measured in a treadmill test. It is suggested that increased dopaminergic neurotransmission may stimulate sexual behavior in an indirect way, augmenting behavioral arousal. The inhibitory effects of dopamine antagonists could be explained either by a reduced arousal level or by motor deficiencies.