GnRH antagonist effects on follicle number and size in rat neonates and infants

Increased levels of gonadotropins in the perinatal and prepubertal period may be responsible for the rapid phase of concurrent follicular atresia. This study tests the hypothesis that follicular atresia during this period can be reduced by suppressing gonadotropin release with a GnRH antagonist. Female rat litter mates were randomized to receive daily injections of GnRHi (100 μg Detirelix^® [Syntex, Palo Alto, CA] from the day of birth and were sacrificed at 5, 15, or 26 days of life. Follicular atresia was assessed by measuring number and size distribution of ovarian follicles. Serum FSH levels were assayed. GnRHi treatment significantly depressed serum FSH and decreased the number of large antral follicles in 26 day rats, while body weight, reproductive tract weight and total follicle number per representative section were not significantly altered. Age-related changes were significant for all variables. The loss of primordial follicles is likely the result of another mechanism or combination of mechanisms. Gonadotropins do not appear to play a major role in follicular atresia in the neonatal and infant rat.