Effects of renal nerves on renal hemodynamics. I. Direct stimulation and carotid occlusion.

Renal nerves were stimulated either directly (loop electrodes) or indirectly (bilateral carotid occlusion with maintenance of control blood pressure) in anesthetized dogs to determine the effects on renal blood flow (RBF), glomerular filtration rate (GFR), sodium excretion (UNaV), and intrarenal distribution of blood flow (microsphere method). Direct nerve stimulation decreased RBF 20% in 9 of 10 dogs; but GFR, UNaV, and intrarenal distribution of blood flow did not change significantly. Carotid occlusion decreased RBF in 9 of 10 dogs. There was a 22% fall in RBF for the whole group, GFR decreased 33%, and UNaV decreased from 0.39 to 0.17 muEq/min/g (p smaller than 0.05). A small (8%) decrease in midcortical fractional flow (p smaller than 0.05 after carotid occlusion was the only distributional flow change observed. The results disclosed no relationship between changes in sodium excretion and changes in total RBF, GFR, or intrarenal distribution of blood flow following nerve stimulation. These studies also indicate that the renal effects of carotid occlusion are probably not mediated by renal nerve stimulation alone.