Haemodynamic responses and renin release during stimulation of afferent renal nerves in the cat.

1. Experiments were done on anaesthetized cats to study the effect of electrical stimulation of afferent renal nerves on the circulatory system and on the release of renin from the kidney. 2. Stimulation of afferent renal nerves over a wide range of parameters consistently elicited an increase in arterial pressure and heart rate. This response was still present in paralysed animals and was not accompanied by changes in respiration or in sympathetic autonomic activity usually associated with painful stimulation. Mesenteric and iliac vasoconstriction was observed concomitantly with the increase in arterial pressure. 3. Release of renin from the contralateral innervated kidney was not significantly changed by stimulation of afferent renal nerves. 4. The existence of renal vascular mechanoreceptors was investigated by altering renal circulation. Stenosis of the renal artery or a marked reduction in renal perfusion pressure elicited an increase in arterial pressure while stenosis of the renal vein elicited a decrease in arterial pressure. These responses, however, were not affected by denervation of the kidney and were therefore interpreted as not being due to neural mechanisms. 5. The precise nature, location and physiological role of renal receptors involved in the cardiovascular responses observed during electrical stimulation of afferent renal nerves remain to be determined.