Brain monoaminergic control of male reproductive behavior. II. Dopamine and the post-ejaculatory refractory period.

This study was designed to examine the role of central dopaminergic mechanisms in the control of copulation and the subsequent post-ejaculatory refractory period in the male rat. Disruption of central dopaminergic pathways was achieved in two separate groups of animals by: (1) selective electrolytic lesions of the substantia nigra (the major locus for dopamine cell bodies in the brain); or (2) localized intracerebral injection of 6-hydroxydopamine, a specific neurotoxin for catecholaminergic pathways. A third group of animals was tested for sexual behavior following administration of the dopamine receptor blocker pimozide. Both electrolytic and neurochemical lesions localized in the substantia nigra produced a significant increase in the length of the post-ejaculatory refractory period. Dopamine receptor blockade following administration of pimozide also caused a significant increase in refractory period duration. These results support the hypothesis that central dopaminergic pathways are involved in the motivational or arousal component of copulation and may be integral to the maintenance of a normal post-ejaculatory refractory period.