Developmental changes in the responsiveness of hypothalamic ER alpha mRNA levels to food deprivation.

OBJECTIVE Estrogen plays an important role in feeding and energy balance, and the critical role of estrogen in the control of appetite and energy balance is mediated by hypothalamic estrogen receptor (ER) alpha. In undernourished rodents, hypothalamic ER alpha mRNA expression are decreased. Responses of some hypothalamic factors to negative energy balance develop during the early neonatal period. DESIGN In this study, we examined the developmental changes of fasting-induced alterations in hypothalamic ER alpha mRNA expression in female rats. RESULTS ER alpha mRNA expression was reduced after a 12-h or 24-h fast at postnatal days 15 and 25, but not at day 5. Serum estradiol levels in postnatal day 25 rats were not changed by fasting. Although serum leptin levels were suppressed by fasting at all ages, hypothalamic ER alpha mRNA expression at postnatal day 25 was not changed by leptin administration after a 24-h fast. CONCLUSIONS These data show that the sensitivity of hypothalamic ER alpha to negative energy balance may not be established in the early neonatal period, and that it develops by postnatal day 15. Decreased leptin levels might not be involved in the alterations of hypothalamic ER alpha mRNA expression in the undernourished condition.