A D 1 Agonist in the MPOA Facilitates Copulation in Male Rats

Abstract

apomorphine, microinjected into the medial preoptic area (MPOA), enhances the copulatory behavior of male rats, while pharmacological blockade of endogenous dopamine inhibits sexual behavior. We now report that MPOA injections of 10 /~g of the selective D ~ agonist dihydroxyphenyl-tetrahydrothienopyridine (THP) significantly increased the number of ejaculations, while decreasing the latency to ejaculate in a 30-min test. These effects were not observed following coadministration of the selective D ~ antagonist SCH-23390 with 10 #g THP. This enhancement may be related to a Dr-stimulated facilitation of penile erections. Dihydroxyphenyl-tetrahydrothienopyridine (THP) Dopamine D ~ receptor Copulation Medial preoptic area DOPAMINERGIC drugs facilitate sexual behavior in men and male rats (3). Copulatory behavior of the male rat is a complex process requiring the integration of genital, motivational, and somatomotor systems. One brain site where dopaminergic activity appears to facilitate all three of the above behavioral factors is the medial preoptic area (MPOA) (15, 20,23). Dopamine in the MPOA influences genital reflexes, probabl