Effects of 5-HT3 agonists on reproductive behaviors in rats

Activity at 5-HT₁ and 5-HT₂ receptor sites influences sexual behavior in male and female rats. 5-HT₃ antagonists reportedly have no effect on copulatory activity in rats of either sex although they influence a variety of other behaviors. The effects of 5-HT₃ agonists on sexual behavior are unknown. The following experiments were undertaken to assess the influence of the 5-HT₃ agonists 1-phenylbiguanide (PBG) and 2-methyl-serotonin (2-Me-5-HT) on sexual behavior, when administered intracerebroventricularly. Consistent with earlier reports indicating that 5-HT₁ and 5-HT₂ receptor activity influences reproductive activity in a sex-dependent manner, PBG was found to facilitate male, but not female, rat sexual behavior. 2-Me-5-HT, however, failed to modify either female or male rat sexual activity. Evidence that PBG, but not 2-Me-5-HT, induces carrier-mediated dopamine release suggests that the effect of PBG in male rats is due to dopaminergic mediation. Overall, the present data indicate that 5-HT₃ receptor activation has only slight effects on rat sexual behavior.