Angiotensin II in the paraventricular nucleus stimulates sympathetic outflow to the cardiovascular system and make vasopressin release in rat

The hypothalamic paraventricular nucleus (PVN) plays essential roles in neuroendocrine and autonomic functions, including cardiovascular regulation. It was shown that microinjection of angiotensin II (Angll) into the PVN produced a pressor response. In this study, we explored the probable mechanisms of this pressor response. AngIl was microinjected into the PVN and cardiovascular responses were recorded. Then, the responses were re-tested after systemic injection of a ganglionic blocker, Hexamethonium, or a vasopressin V-1 receptor blocker. Hexamethonium pretreatment (i.v.) greatly and significantly attenuated the pressor response to AngII, with no significant effect on heart rate, indicating that the sympathetic system is involved in the cardiovascular effect of AnglI in the PVN. Systemic pretreatment (i.v.) with V1 antagonist greatly and significantly attenuated the pressor response to AngII, with no significant effect on heart rate, indicating that vasopressin release is involved in the cardiovascular effect of AngII in the PVN. Overall, we found that AnglI microinjected into the PVN produced a pressor response mediated by the sympathetic system and vasopressin release, indicating that other than circulating Angll, endogenous AngII of the PVN increases the vasopressin release from the PVN. (C) 2016 Elsevier Ireland Ltd. All rights reserved.