Influences of 5-hydroxytriptamine on sperm hyperactivation and in vitro fertility in rats

The neurotransmitter, 5-hydroxytriptamine (5-HT), is well known. Furthermore, it enhances the acrosome reaction, hyperactivation, and in vitro fertilization (IVF) success in hamsters and mice. In the present study, we examined whether 5-HT enhances hyperactivation and increases IVF success in rats. When rat sperm was exposed to 5-HT, hyperactivation was significantly enhanced. Only the 5-HT₄ receptor agonists significantly enhanced hyperactivation. Additionally, both 5-HT and 5-HT₄ receptor agonists significantly increase the success of IVF. These results suggested that 5-HT increases IVF success by enhancing hyperactivation and effects of 5-HT are associated with the 5-HT₄ receptor. Therefore, in rats, 5-HT enhances capacitation and the 5-HT₄ receptor is the key molecule for capacitation.