Differential renal and splenic nerve responses to vagal and spinal afferent inputs.

Specific contributions of the kidney and spleen to cardiovascular homeostasis may be determined partially by differential sympathetic influences on each organ. This investigation was a comparison of renal and splenic sympathetic responses to stimulation of vagally innervated cardiac receptors and receptors of abdominal visceral and muscle spinal afferent nerves. Experiments were performed in anesthetized, sinoaortic-denervated cats in which upper thoracic sympathetic ganglia had been removed. Left atrial injections of veratridine depressed renal and splenic nerve discharges by 68 and 44%, respectively. In contrast, injections of bradykinin into the abdominal aorta caused 18 and 104% excitation of renal and splenic nerves, respectively. Visceral ischemia and mesenteric stretch by snare occlusion of the celiac artery caused 20 and 64% excitation of renal and splenic nerves, respectively. Left atrial injections of bradykinin caused biphasic renal nerve responses (range, 200% excitation to complete inhibition) and 246% excitation of splenic nerves; after vagotomy both renal and splenic nerves were excited (21 and 117%, respectively). In conclusion, sympathetic control of the kidney and spleen can be selective, illustrating significant potential discreteness of sympathetic outflow to the viscera.