D1-like antagonist blocks conditioned place preference induced by ejaculation in male rats

Mating behavior, particularly ejaculation, induces a state of sexual reward, which is evaluated by the conditioned place preference test. Several studies have shown that opioid receptors are involved in inducing the state of sexual reward, mainly because this state is blocked with naloxone, a mu opioid receptor antagonist. Dopamine has been implicated in sexual motivation, coital behavior and sexual reward, however, some experiments show that D2-like or non-specific dopaminergic antagonists are not capable of blocking the conditioned place preference induced by ejaculation; therefore, the role of dopamine on sexual reward has not been demonstrated, or has been frequently discarded. We show that a dose of SCH 23390 (a specific dopamine D1-like receptor antagonist), which does not modify locomotion, blocks the conditioned place preference induced by ejaculation and the conditioned place preference induced by SKF 38393 (D1-like agonist). Our results indicate that dopamine, across the D1-like receptors, is involved in the sexual reward induced by ejaculation.