SEXUAL ATTRACTION AND COPULATION IN MALE-RATS - EFFECTS OF THE DOPAMINE AGONIST SND-919

Behavioral differences towards receptive females, involving latency to the first contact, amicable behavior, genital exploration, and copula tory pattern, were seen in sexually active (A), sluggish (S), and inac tive (I) male rats classified on the basis of 11 consecutive mating te sts. The D-2 dopamine agonist SND 919 (1 mg/kg) was intraperitoneally administered to the three groups 25 min before a 12th test; the drug s timulated the copulatory behavior of A and S but not of I rats in whic h it diminished genital exploration and amicable behavior. In a 13th t est, conducted 1 week later, 31% of I initiated mating, 16% of them re aching ejaculation. The stimulant effect of SND 919 on copulation in A rats was confirmed in further experiments where it was injected at 0. 1 mg/kg, a dose selective for the D-2 autoreceptors.