A D-1 AGONIST IN THE MPOA FACILITATES COPULATION IN MALE-RATS

The classic dopamine agonist apomorphine, microinjected into the media l 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 mu g of the select ive D-1 agonist dihydroxyphenyl-tetrahydrothienopyridine (THP) signifi cantly increased the number of ejaculations, while decreasing the late ncy to ejaculate in a 30-min test. These effects were not observed fol lowing coadministration of the selective D-1 antagonist SCH-23390 with 10 mu g THP. This enhancement may be related to a D-1-stimulated faci litation of penile erections.