ANESTHESIA DURING HORMONE ADMINISTRATION ABOLISHES THE ESTROGEN INDUCTION OF PREPROENKEPHALIN MESSENGER-RNA IN VENTROMEDIAL HYPOTHALAMUS OFFEMALE RATS

Estrogen treatment increases preproenkephalin (PPE) mRNA levels in the ventromedial nucleus of the hypothalamus (VMH). Roy et al. (Brain Res ., 337 (1985) 163-166) discovered that anesthesia during estrogen prim ing could reduce female rat sexual receptivity. In the present study w e tested whether the action of estrogen to induce PPE gene expression in the VMH could be similarly affected by anesthesia. By quantitative in situ hybridization and slot-blot analysis techniques we found a 1.8 -fold increase in PPE mRNA levels in the VMH after 1 hour of estrogen treatment in ovariectomized (OVX) Sprague-Dawley female rats. Anesthet izing the rats with pentobarbital for 1 h during the exposure to estro gen blocked the estrogen induction of PPE mRNA in the VMH. By way of c ontrast no changes in the PPE mRNA levels were observed in the caudate putamen. A similar trend was seen using chloral hydrate. It appears t hat neuronal activity is required for the early phase of estrogen indu ction of PPE mRNA levels in the VMH. This in turn could be correlated with changes in female sociosexual behaviors.