Role of nitric oxide and angiotensin II in the regulation of sympathetic nerve activity in spontaneously hypertensive rats.

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Abstract
This study evaluated the actions of nitric oxide on the blood pressure and renal sympathetic nerve activity responses produced by angiotensin II (Ang II) blockade in conscious spontaneously hypertensive rats. Two days after implantation of electrodes, we measured mean arterial pressure, heart rate, and renal sympathetic nerve activity. Baroreceptor reflex function was assessed with a logistic function curve; the maximum slope of the curve estimated the baroreceptor reflex gain. Data were obtained in rats given acute intravenous administration of either vehicle, the Ang II type 1 receptor antagonist losartan, the type 2 antagonist CGP 42112A, or the converting enzyme inhibitor lisinopril. In comparison with vehicle (-1.1 +/- 0.2%/mm Hg), both losartan (-1.8 +/- 0.3%/mm Hg) and lisinopril (-2.4 +/- 0.2%/mm Hg) significantly increased the maximum gain of the baroreceptor reflex control of nerve activity (p < 0.05). In contrast, the type 2 receptor antagonist did not alter baroreceptor reflex function. Simila...