ADRENAL-STEROID REGULATION OF CENTRAL ANGIOTENSIN-II RECEPTOR SUBTYPES AND OXYTOCIN RECEPTORS IN RAT-BRAIN

The neuropeptides angiotensin II (AngII) and oxytocin (OT) play import ant but opposing roles in the regulation of sodium appetite in the rat , AngII as a stimulatory peptide and OT as an inhibitory peptide. Adre nal steroids increase the density of AngII receptors in brain followin g in vivo administration, although the neuroanatomical and subtype spe cificity have not been thoroughly examined. Furthermore, previous stud ies demonstrate that adrenalectomy (ADX) leads to a reduction in OT re ceptors, although regions associated with sodium appetite remain to be examined. In the present study, quantitative receptor autoradiography was used to locate regions where perturbations in circulating adrenal steroids affect the density of oxytocin receptors and the angiotensin receptor subtypes AT1 and AT2. The results show that ADX results in a small, but significant decrease in AT1 expression in the paraventricu lar nucleus of the hypothalamus, subfornical organ, and the area postr ema. That this effect is reversed by either aldosterone or low-dose co rticosterone replacement suggests that occupancy of the mineralocortic oid receptor is responsible for the steroid effect. No changes were ob served in AT2 or OT receptors in nuclei associated with sodium appetit e, indicating that perturbations in adrenal steroids did not affect th ese receptors in brain regions implicated in the control of salt appet ite. (C) 1998 Elsevier Science B.V. All rights reserved.