INTRAVASCULAR MECHANORECEPTOR MODULATION OF RENAL SYMPATHETIC NERVE ACTIVITY

Experiments were performed in the anesthetized primate Macaca fascicularis and the domestic cat to characterize the influence of high and low pressure intravascular receptors on renal nerve activity. Epinephrine induced rises in arterial pressure were used to stimulate high pressure receptors and intravascular volume expansion was used to stimulate both high and low pressure receptors. The intravascular mechanoreceptors were stimulated directly with intravenous veratrine administration. All interventions produced large decreases in renal nerve activity in the intact state. Denervation of the carotid sinus or bilateral cervical vagotomy diminished, while sino-aortic denervation with vagotomy completely abolished all responses of renal nerve activity to these interventions. Inflation of a balloon in the left atrium of the intact monkey resulted in increased left atrial pressure and decreased arterial pressure with variable responses of renal nerve activity. Balloon inflation after vagotomy consistently increased renal nerve activity while balloon inflation after sino-aortic denervation consistently decreased renal nerve activity. These experiments demonstrate a significant influence and interplay of high and low pressure receptors on renal nerve activity. Baroreceptor afferents in the carotid sinus nerves and the vago-aortic trunks appear to be equally effective in inhibiting renal nerve activity in response to rises in arterial pressure. No evidence was found for a significant contribution from sympathetic afferent nerves to the reflex modulation of renal nerve activity.