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

Increased levels of gonadotropins in the perinatal and prepubertal period m ay be responsible for the rapid phase of concurrent follicular atresia. Thi s study tests the hypothesis that follicular atresia during this period can be reduced by suppressing gonadotropin release with a GnRH antagonist. Fem ale rat litter mates were randomized to receive daily injections of GnRHi ( 100 mu g Detirelix(R) [Syntex, Pale Alto, CA] from the day of birth and wer e sacrificed at 5, 15, or 26 days of lire. Follicular atresia was assessed by measuring number and size distribution of ovarian follicles. Serum FSH l evels were assayed. GnRHi treatment significantly depressed serum FSH and d ecreased the number of large antral follicles in 26 day rats, while body we ight, reproductive tract weight and total follicle number per representativ e section were not significantly altered. Age-related changes were signific ant for all variables. The loss of primordial follicles is likely the resul t of another mechanism or combination of mechanisms. Gonadotropins do not a ppear to play a major role in follicular atresia in the neonatal and infant rat.