Induction of mating behavior by apomorphine in sexually sated rats

We have tested the hypothesis, suggested by our previous neurochemical studies, that the inhibition of sexual behavior that follows unrestricted mating could be caused by a blockade of dopaminergic transmission. Male rats were allowed to copulate until they reached a satiety criterion. The following day, after verification that they were sexually inactive, the animals were injected with the dopamine agonist, apomorphine, at doses of 80, 200, and 500 micrograms/kg body weight and their behavior with receptive females was recorded. A bell-shaped dose-response curve was found, with the 200 micrograms/kg dose having the maximal stimulatory effects on mating. Whereas these findings seem to support the above hypothesis, it should be noted that apomorphine treatments were unable to restore fully the copulatory pattern shown by sexually rested animals. This could be due to several factors including the interference of apomorphine-induced stereotypies, and/or the involvement of additional transmitter systems in the mechanisms of sexual satiety.