Intravascular mechanoreceptor modulation of renal sympathetic nerve activity in the cat

Experiments were performed in chloralose-anesthetized cats to characterize intravascular mechanoreceptro input to renal nerve activity in the intact and vagotomized sinoaortic-denervated states. High-pressure intravascular mechanoreceptors were stimulated by rises in arterial pressure caused by norepinephrine. Low-pressure intravascular mechanoreceptors were stimulated by progressive blood volume expansion (14-23%) at a rate of 4.4 or 17.6 ml/min. In addition, veratrine was used to stimulate directly both high- and low-pressure receptors. In the intact animal the administration of norepinephrine or blood volume expansion was associated with substantial decreases in renal nerve activity. Veratrine also caused a large dose-related decrease in renal nerve activity. However, in the vagotomized sinoaortic-denervated animal there was no change in renal nerve activity with norepinephrine, volume expansion, or veratrine administration. These experiments demonstrate that the major afferent pathways for renal sympathetic circulatory reflexes are confined to the carotid sinus and aortic and vagus nerves. No evidence was found for a significant contribution from sympathetic afferent nerves.