Different pharmacological anatomy in the paraventricular hypothalamic nucleus,supraoptic nucleus,and suprachiasmatic nucleus of rats: Quantitative autoradiography on angiotensin II receptor binding sites

Angiotensin II (AII) and vasopressin (VP) play important roles in cardiovascular function. Using ¹²⁵I-[Sar¹, Ile⁸]-angiotensin II (¹²⁵I-SI-AII), a potent AII antagonist, AII receptor binding sites were autoradiographically localized in three VP-producing areas of the hypothalamus and compared in hypertensive and normotensive rats. Within three major VP-producing areas, AII receptor binding was highest in the paraventricular hypothalamic nucleus and lowest in the supraoptic nucleus, suggesting that a differential AII regulation of separate VP systems exists in the brainstem. No statistical difference in ¹²⁵I-SI-AII receptor binding was found between WKY and SHR rats in each of the three major VP-producing nuclei studied. These results are consistent with a role of AII receptors in a subtle and complicated regulation of VP in cardiovascular function.