Neural control of renal circulation.

It has long been appreciated that renal nerves influence renal hemodynamics. Direct or reflex activation of renal nerves causes vasoconstriction, with the degree of vasoconstriction being proportional to the magnitude of stimulation. Conversely, removal of enhanced nerve activity ameliorates renal vasoconstriction. The effector loci within the renal microcirculation have been identified and include afferent and efferent arterioles as well as the glomerular capillary bed itself. The hemodynamic changes have been corroborated by morphological studies which reveal that the lumen of arterioles constrict and the glomerular capillary tuft contracts following an increase in neural activity. Moreover, mesangial cells, which are the putative vectors of regulation of hemodynamics within the glomerular capillary bed, constrict in response to the neurotransmitter, norepinephrine.