Renal nerve and blood pressure responses to stimulation of cardiac receptors in dogs and cats by bradykinin

It has been recently demonstrated in anesthetized, sinoaortic denervated-vagotomized (SAD+V_x) cats that epicardial or intracoronary (IC) bradykinin (BK) evokes an increase in efferent renal nerve activity (RNA) and a pressor response which is mediated by the cardiac sympathetic afferent nerves. The purpose of this study was to compare the effect of epicardial, IC, and left atrial (LA) administration of BK on arterial blood pressure (ABP) and RNA in intact and SAD+V_x cats and dogs. A total of seven cats and eight dogs anesthetized with chloralose were prepared with a left circumflex coronary arterial catheter (dogs) or a LA catheter (cats). Changes in ABP and RNA were determined in both dogs and cats when 1 to 100 μg/ml of BK was applied to the anterior surface of the left ventricle or injected IC or LA (0.3 and 3.0 μg/kg BK) in the intact and SAD+V_x state. In both the intact and SAD +V_x cat, a pressor response was consistently elicited with epicardial BK. In the SAD+V_x state, epicardial BK increased ABP by 33.4±4.7 mm Hg (p<.001). RNA followed this same trend showing a consistent and significant increase with both LA and epicardial BK (+24.8±8.4% in the SAD+V_x state; P<.05). Changes in RNA in dogs were highly variable with epicardial and IC BK in intact and in SAD V_x dogs, resulting in insignificant changes in this parameter. The results of this study demonstrate that the reflex effects of stimulation of cardiac sympathetic afferents by BK are species specific and need not evoke an increase in peripheral sympathetic outflow.