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-pituitary (HP) axis, as well as an increased demand for food and water. The renin-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 lactation and diestrus. Compared with diestrus, lactating rats had significant decreases in ANG II receptor binding in several forebrain regions, most notably in the arcuate nucleus/median eminence, dorsomedial hypothalamic nucleus (DMH), and lateral hypothalamic area (LHA). In contrast, there was an increase in ANG II receptor binding in the preoptic area during lactation. These significant changes in ANG II binding in the brain during lactation support the hypothesis that changes in the RAS may contribute to the dramatic changes in the HP axis during lactation. In addition, the significant reduction 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 RAS.