Renal nerve and cardiovascular responses to cardiac receptor stimulation in rabbits

It has been shown that a species difference exists among cats, dogs, and monkeys in the reflex response to cardiac sympathetic afferent stimulation with bradykinin (BK). This study was performed to determine the arterial blood pressure (ABP), heart rate (HR), and renal nerve activity (RNA) responses to epicardial BK applications in the intact and sinoaortic-denervated and vagotomized (SAD + Vx) rabbits. Eight rabbits were anesthetized with pentobarbital sodium. The heart was exposed and suspended in the epicardial cradle. The ABP, HR, and RNA responses were determined when 1 and 10 micrograms/ml BK were applied to the anterior surface of the left ventricle in the intact and SAD + Vx state. In both the intact and SAD + Vx rabbits, ABP, HR, and RNA were significantly reduced with epicardial BK. In the SAD + Vx rabbits, BK evoked small decreases in ABP and HR and no change in RNA after topical lidocaine. These results show the existence of a depressor response and decreases in HR and RNA in the rabbit mediated by the action of BK on cardiac sympathetic afferents.