Sympathetic modulation of renal hemodynamics, renin release and sodium excretion.

In anesthetized animals it has been shown previously, that the influence of electrical stimulation of efferent renal nerves on renal function with increasing stimulation frequencies can be graded; renin release is affected at low, sodium excretion at intermediate and vascular resistance at high stimulation frequencies. Experiments in conscious dogs are reviewed, which present evidence for a similar functional dissociation under physiological conditions. Moderate activations of the renal sympathetic nerves, which do not change renal blood flow 1) decrease sodium excretion independent of changes in angiotensin II, 2) interact with the pressure-dependent mechanism of renin release by resetting its threshold pressure and 3) modulate autoregulation by increasing the lower limits of glomerular filtration rate and renal blood flow-autoregulation. These findings may contribute to our understanding of the role of the renal nerves in the pathophysiology of congestive heart failure and hypertension.