Neural control of renin secretion in anesthetized dogs. Interaction of cardiopulmonary and carotid baroreceptors.

Vagal cold block increased arterial blood pressure but not the secretion of renin (radioimmunoassay) in 17 of 20 anesthetized mechanically ventilated dogs with aortic nerves cut and carotid sinuses intact.Vagal block caused an increase in renin secretion in four dogs with aortic nerves cut when the carotid sinuses were vascularly isolated; this was abolished or greatly attenuated when the carotid baroreflex was allowed to function normally.In five dogs with aortic nerves cut, vagal cold block caused an increase in arterial blood pressure and in inhibitory nerve traffic from the carotid baroreceptors.In 7 of 10 dogs, a nonhypotensive hemorrhage (4 ml/kg) increased renin secretion before but not after vagotomy.Nine of 11 dogs released renin during hemorrhage before and after sham vagotomy.Inhibitory traffic from carotid sinus baroreceptors was not decreased by nonhypotensive hemorrhage.The experiments show that (1) cardiopulmonary receptors with vagal afferents exert a tonic inhibition of renin secretion in the presence of normally functioning carotid baroreceptors; (2) cardiopulmonary receptors can respond to a decrease in blood volume to which arterial baroreceptors are insensitive; and (3) when free to exert their normal buffering influence, carotid baroreceptors can markedly or totally inhibit the release of renin which results from complete interruption of afferent vagal traffic from cardiopulmonary receptors.The study shows that the reflex change in renin secretion may vary, depending on whether only one receptor system is involved or whether two or more systems interact in response to the disturbance.