HORMONAL PRIMING AND TRIGGERING OF MATERNAL-BEHAVIOR IN THE RAT WITH SPECIAL REFERENCE TO THE RELATIONS BETWEEN ESTROGEN-RECEPTOR BINDING AND ER MESSENGER-RNA IN SPECIFIC BRAIN-REGIONS

Estrogen stimulation of maternal behavior during pregnancy in the rat has been studied at several levels of analysis. These include (a) chan ges in maternal responsiveness during pregnancy, (b) hormonal stimulat ion of maternal behavior; and (c) correlation between nuclear binding of estradiol in the medial preoptic area and the stimulation of matern al behavior (i.e., in pregnancy-terminated, ovariectomized females tre ated with estradiol benzoate). These studies have given rise to the co ncepts of hormonal priming and triggering of maternal behavior during pregnancy and at parturition. More recently, using in situ hybridizati on, ER mRNA was measured during pregnancy (also diestrus and postpartu m) in brain regions in which binding previously had been studied, to i nvestigate further the regulation of hormonal priming. Steady state le vels of ER mRNA per cell and cell densities of ER mRNA produced a meas ure of total ER mRNA per brain region which was then compared to nucle ar estrogen receptor binding. The relation between binding and ER mRNA is presented for one of the brain regions, the rostral medial preopti c nucleus. The results indicate that ER transcription is regulated dur ing pregnancy, but regulation is specific to each brain region and the re is no simple relation between ER mRNA and nuclear estrogen receptor binding.