The effects of indoleamines (serotonin and melatonin) on induction of ovulation in rabbits.

Serotonin as well as melatonin introduced into the 3-rd cerebral ventricle in doses of 120 mug blocked induction of ovulation in rabbits; it was also observed that the ovulation-blocking effect of serotonin was much more effective than that of melatonin. The inhibitory effect of both indolamines on this process was more evident in summer than in spring. The role of serotonin and melatonin as mediators blocking the release of hypothalamic gonadotropin-releasing hormones (GRH) and the participation of these amines in the regulation of seasonal sexual rhythms are discussed.