Functional identification of the central projections of afferent renal nerves

The central integration of cardiovascular reflexes produced by activation of renal sensory mechanisms was examined by studying arterial pressure and regional blood flow responses to electrical stimulation of the renal afferent nerves. Spinal transection, rostral to the entry into the cord of renal afferent projections, abolished the cardiovascular response consisting of an a fall in arterial pressure, mesenteric vasoconstriction and vasodilation in the hindquarters. Several supraspinal structures at medullary, midbrain and forebrain levels were identified by lesion studies to be important for the reflex responses. Lesion of NTS abolished the hindquarter vasodilator response but left the mesenteric vasoconstrictor response intact. Lesions of the parabrachial complex produce similar effects whereas lesions in the periventricular preoptic region of hypothalamus abolished mesenteric vasoconstriction and left hindquarter vasodilation unaffected. These studies demonstrate that cardiovascular reflexes elicited by activation of renal sensory nerves require integrity of spinal pathways and are differentially integrated at several levels of the neuraxis.