Reinforcing properties of ejaculation in the male rat: Role of opioids and dopamine.

It is suggested that release of endogenous opioids renders ejaculation rewarding, and dopamine seems to be of slight importance for that effect of copulation.

Abstract

Ejaculation-induced reward in the male rat was evaluated by the conditioned place-preference paradigm. It was supposed that ejaculation induces a reward state such that it can be conditioned to environmental stimuli. Males were allowed to ejaculate once and were then immediately transferred to a place-preference cage. One ejaculation produced place preference. Naloxone (16 mg/kg) not only blocked this place preference but also induced a place aversion. Naloxone by itself had no effect on place preference. It is suggested that release of endogenous opioids renders ejaculation rewarding. Pimozide, in a dose of 1 mg/kg, had no effect on ejaculation-induced reward. Dopamine thus seems to be of slight importance for that effect of copulation. Perhaps compulsive sexual activity obeys the same mechanisms as compulsive drug use in opiate addicts.