Melatonin Exerts Stimulatory Effect on Human Sperm Motility, In Vitro

Pineal indolic compounds have been postulated to play an antigonadotrophic role in the reproductive system of mammals. In humans, indoleamines are localized in tissue fluids such as plasma, serum, cerebrospinal fluid, aqueous humor, semen, and follicular fluid. Because they exhibit antigonadotrophic properties, we examined whether melatonin causes any inhibitory effects on sperm motility. In the present study, significant stimulation of sperm motility by this indole was observed. Furthermore, the presence of melatonin in incubation medium did not decrease, but on the contrary increased sperm velocity slightly and nonsignificantly. These data raise the possibility that the presence of high doses of indoles in reproductive fluids may increase sperm motility and velocity. This stimulatory effect of melatonin on sperm motility parameters was concluded to be due to its action as a highly efficient free radical scavenger and general antioxidant.