Abstract

NADPH oxidase-generated reactive oxygen species (ROS) are highly implicated in the development of angiotensin II (AngII)-dependent hypertension mediated in part through the hypothalamic paraventricular nucleus (PVN). This region contains vasopressin and non-vasopressin neurons that are responsive to cardiovascular dysregulation, but it is not known whether ROS is generated by one or both cell types in response to “slow-pressor” infusion of AngII. We addressed this question using ROS imaging and electron microscopic dual labeling for vasopressin and p47^phox, a cytoplasmic NADPH oxidase subunit requiring mobilization to membranes for the initiation of ROS production. C57BL/6 mice or vasopressin-enhanced green fluorescent protein (VP–eGFP) mice were infused systemically with saline or AngII (600 ng · kg⁻¹ · min⁻¹, s.c.) for 2 weeks, during which they slowly developed hypertension. Ultrastructural analysis of the PVN demonstrated p47^phox immunolabeling in many glial and neuronal profiles, most of which were postsynaptic dendrites. Compared with saline, AngII recipient mice had a significant increase in p47^phox immunolabeling on endomembranes just beneath the plasmalemmal surface (+42.1 ± 11.3%; p < 0.05) in non-vasopressin dendrites. In contrast, AngII infusion decreased p47^phox immunolabeling on the plasma membrane (−35.5 ± 16.5%; p < 0.05) in vasopressin dendrites. Isolated non-VP–eGFP neurons from the PVN of AngII-infused mice also showed an increase in baseline ROS production not seen in VP–eGFP neurons. Our results suggest that chronic low-dose AngII may offset the homeostatic control of blood pressure by differentially affecting membrane assembly of NADPH oxidase and ROS production in vasopressin and non-vasopressin neurons located within the PVN.