A comparison of brain angiotensin II receptors during lactation and diestrus of the estrous cycle in the rat

During lactation there are many dramatic alterations in the hypothalamic-pi tuitary (HP) axis, as well as an increased demand for food and water. The r enin-angiotensin system (RAS) is one of the major mediators of the HP axis. This study examined the receptors for ANG II in the rat brain during lacta tion and diestrus. Compared with diestrus, lactating rats had significant d ecreases in ANG II receptor binding in several forebrain regions, most nota bly in the arcuate nucleus/median eminence, dorsomedial hypothalamic nucleu s (DMH), and lateral hypothalamic area (LHA). In contrast, there was an inc rease in ANG II receptor binding in the preoptic area during lactation. The se significant changes in ANG II binding in the brain during lactation supp ort the hypothesis that changes in the RAS may contribute to the dramatic c hanges in the HP axis during lactation. In addition, the significant reduct ion in ANG II binding in the DMH and LHA may be indicative of a role in the regulation of food intake, a function only recently associated with the RA S.