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 release by angiotensin II (AngII). In the present study, AT(2) receptor-directed antiserum immunohistochemically detected AT(2) receptors within the hypothalamic paraventricular (PVN) and the supraoptic nuclei (SON) of the rat brain, more specifically, in identified vasopressinergic neurons. Considering the lack of AT(2) binding in the PVN and the SON using receptor autoradiography, we tested the hypothesis that these AT(2) receptors are transported to the posterior pituitary. Western blot analysis detected AT(2) immunoreactivity in the posterior pituitary. However, no AT(2) binding was detected in posterior pituitary membranes, and no AT(2) binding was detected with quantitative receptor autoradiography in the neurohypophysis. Thus, if AT(2) receptors are transported from the magnocellular vasopressin neurons to the posterior pituitary, their role in AngII regulation of vasopressin release at the neurohypophyseal terminals remains to be clarified. (C) 1998 Elsevier Science B.V.