Serotonin Suppression of Luteinization in Gonadotrophin-Treated, Immature Rats

Effects of serotonin on the ovulatory cycle have been studied in immature female rats treated with pregnant mares' serum gonadotropin (PMS). In 24-day-old rats a single injection of PMS causes follicular development, ovulation and luteinization. Injections of either 12.5 or 25.0 mg/kg body weight of serotonin daily for 5 days after PMS treatment inhibited luteinization and ovarian weight increases. A single injection of 25.0 mg/kg serotonin administered at 51 hr after PMS caused a similar inhibition. Subcutaneous injections of PMS and human chorionic gonadotropin, which has LH-like activity, caused ovulation and luteinization in the ovary, even after serotonin treatment. These findings are interpreted as indicating a serotonin inhibition of luteinization, not on the ovary directly, but through the suppression of the mechanisms involving LH release either in the hypophysis or in the central nervous system. (Endocrinology74: 885, 1964)