Circulation research
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Circulation research · Mar 1990
Comparative StudyImportance of endogenous angiotensin II in the cardiovascular responses to sympathetic stimulation in conscious rabbits.
Pharmacological evidence indicates that angiotensin (Ang II) converting enzyme inhibitors attenuate cardiovascular responses to sympathetic stimulation. To investigate the physiological significance of this attenuation, the pressor and heart rate responses to bilateral carotid occlusion (BCO) were studied before and after administration of captopril and again during Ang II replacement in conscious, aortic nerve-sectioned rabbits with chronically implanted carotid occluders. In the control period, BCO produced increases (p less than 0.05) in mean arterial pressure (MAP) and heart rate (HR) of 37.3 +/- 3.0 mm Hg and 21.7 +/- 5.4 beats/min from baseline values of 79.1 +/- 2.5 mm Hg and 255.4 +/- 16.7 beats/min. ⋯ The response was reduced by less than 40%, indicating only a modest postsynaptic component to the action of captopril. These results provide physiological evidence for an important action of endogenous Ang II in facilitating the cardiovascular responses to sympathetic stimulation in conscious rabbits. This facilitation is not due to an action upon the baroreflex per se but results, at least in part, from a presynaptic action of Ang II.