Effect of neonatal androgenization on positive feedback in female mice.

Exposure of female mice to androgens within 5 days of birth impairs fertility. Such treatment in rats results in a post-pubertal acyclic state of persistent vaginal cornification and in an inability, when ovariectomized, to show normal positive feedback on luteinizing hormone (LH) release in response to steroid challenge. In the present study, we explored whether neonatally androgenized mice demonstrate positive feedback. Female mice were administered 100 micrograms of testosterone propionate (TP) on either Day 1 (TP1) or Day 5 (TP5) after birth, or vehicle on Day 1 (SO1). Androgen-treated mice had a statistically significant advance in onset of vaginal opening as compared with vehicle-treated mice. All mice that received TP entered constant vaginal estrus, whereas those given vehicle showed variable cytology. All mice were ovariectomized at 7 wk of age and received Silastic capsules containing a priming dose of 17 beta-estradiol. When all mice were challenged 1 wk later with sequential administration of estradiol benzoate and progesterone, a significant increase in plasma LH level was present only in the vehicle-treated mice. We conclude that neonatal androgenization defeminizes the neuroendocrine mechanisms controlling gonadotropin release.