The effects of estradiol on gonadotropin-releasing hormone neurons in the developing mouse brain

The hypothalamic-pituitary-gonadal (HPG) axis plays a critical role in the control of reproduction. Two key hormonal components of the HPG axis are go nadal steroids and gonadotropin-releasing hormone (GnRH). Gonadal steroids are known to organize the development of neural substrates which control ad ult reproductive behavior; GnRH is required for normal reproductive structu re and function. The possibility that gonadal steroids may produce organiza tional changes in the pattern of GnRH staining observed in the brain is inv estigated through the use of injections of estradiol to neonatal mice and s ubsequent GnRH immunocytochemistry at 2 months of age. Our results indicate that the number of GnRH-immunoreactive (GnRH-ir) cells is normally lower i n females than males. Estradiol did not affect the number of GnRH-ir cells in females, but significantly increased the number of GnRH-ir cells in male s, suggesting that early exposure to estradiol results in masculinization o f the GnRH axis of males. (C) 1998 Academic Press.