Expression of estrogen receptor alpha in developing brain, ovary and shell gland of Gallus gallus domesticus: Impact of stress and estrogen

Abstract

Estrogen plays a central role in the control of reproductive behaviour and in the regulation of neuroendocrine system. To elucidate the mechanism by which it controls the stress-modulated functions, it is important to understand how estrogenic effects are mediated. The distribution of estrogen receptor alpha (ERα) protein in brain, ovary and shell gland of chickens has been investigated. Immature chickens were taken and randomly divided into four groups. First group served as control (C), second water deprived for two days (WD), third treated with estradiol benzoate (E) and fourth treated with estradiol benzoate followed by water deprivation during last two days of treatment (E + WD). The dose of estradiol benzoate administered for 15 days was 0.5 mg/100 g. Immuno-fluorescent localization demonstrated the presence of ER alpha (ERα) in hypothalamic area, principally the pre-optic area on estrogen administration. However, ERα expression in brain decreased on water deprivation. ERα expression was observed highly in granulosa and thecal cells of E and E + WD ovary compared to immature while least on water deprivation. Similarly, ERα expression was abundant in tunica muscularis and epithelial cells of E and E + WD shell gland while lesser in WD. Plasma estradiol significantly increased in E and E + WD group while decreased on water deprivation. Plasma corticosterone decreased significantly in E and E + WD group while increased in WD. Therefore, we conclude that administration of estradiol in stress decreases corticosterone induced sensitivity mediated by an increased expression of ERα in brain, ovary and shell gland. It appears that negative feedback regulation is involved between HPA-axis and HPG- axis during stress in chickens.