Behavioral effects induced by the dopamine D3 agonist 7-OH-DPAT in sexually-active and -inactive male rats

The present study investigates the effects induced by the putative DA D3 agonist 7-OH-DPAT (0.1 and 1 mg/kg, s.c.) on: (1) the sexual behavior of male rats, categorized on the basis of seven consecutive mating pre-tests as sexually-active (SA) and sexually-inactive (SI); and (2) stretching-yawning, penile erection, sedation and stereotyped behavior of the same animals. The data obtained show that 7-OH-DPAT at both doses modifies the copulatory pattern of SA rats, facilitating ejaculation mechanisms, but fails to increase the sexual drive of the animals as is evident from the ineffectiveness in SI rats. The second major finding is that the two groups of rats, which are markedly different as regards sexual typology, exhibit different behavioral responses to 7-OH-DPAT.