In the adult sexually experienced male rat, the intracerebroventricular (i.c.v.) injection of pinacidil, a K A T P channel opener, at the dose of 100 - 150 - 300 μg/rat worsened the copulatory performance in the presence of a receptive female, whereas the administration of glibenclamide, a K A T P channel blocker, at the dose of 0.5 and 3 mg/kg intraperitoneally (i.p.) had an improving effect. These data indicate that K A T P channels in target neurons may play an important role in the physiology of male sexual behavior.