ANALYSIS OF ANGIOTENSIN TYPE-2 RECEPTORS IN VASOPRESSINERGIC NEURONS AND PITUITARY IN THE RAT

Previous functional studies indicated that an angiotensin type 2 (AT(2 )) receptor subtype may participate in the regulation of vasopressin r elease by angiotensin II (AngII). In the present study, AT(2) receptor -directed antiserum immunohistochemically detected AT(2) receptors wit hin the hypothalamic paraventricular (PVN) and the supraoptic nuclei ( SON) of the rat brain, more specifically, in identified vasopressinerg ic neurons. Considering the lack of AT(2) binding in the PVN and the S ON using receptor autoradiography, we tested the hypothesis that these AT(2) receptors are transported to the posterior pituitary. Western b lot analysis detected AT(2) immunoreactivity in the posterior pituitar y. However, no AT(2) binding was detected in posterior pituitary membr anes, and no AT(2) binding was detected with quantitative receptor aut oradiography in the neurohypophysis. Thus, if AT(2) receptors are tran sported from the magnocellular vasopressin neurons to the posterior pi tuitary, their role in AngII regulation of vasopressin release at the neurohypophyseal terminals remains to be clarified. (C) 1998 Elsevier Science B.V.