Structural and functional neurobiology of renal nerves: A platform for neuromodulation of renal function

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Project Summary Design of neuromodulatory devices targeting the kidney requires detailed knowledge of the structural and functional neurobiology of renal nerves. Our current understanding is fairly rudimentary and based on classical but outdated methodologies. For example, it is generally agreed that renal efferent nerves increase renin release, stimulate sodium reabsorption, and decrease GFR secondary to arteriolar constriction. However, the dose-response relationships for these effects are based on supramaximal electrical stimulation of renal nerves in anesthetized animals. Recent studies in conscious animals suggest this dogma may be incorrect. Even less is known regarding the structural and functional neurobiology of renal afferent nerves. Although it is well accepted that the renal pelvic wall in densely innervated, preliminary findings in our laboratory, as well as reports by others, suggest sensory nerves may also innervate vascular and tubular targets throughout the kidney. However, the physiological role of renal afferent nerves is unclear. Finally, it is well established that the afferent and efferent innervation of the kidney is heterogeneous. Distinct subsets of sympathetic renal nerves express the neuropeptides NPY and VIP. In the afferent renal innervation there is partial overlap of expression of the neuropeptides CGRP and SP and the capsaicin receptor TRPV1. In addition, our preliminary results demonstrate for the first time the presence of renal afferent nerves that express the sensory neuron-specific voltage-gated Na+ channel NaV1.8. The functional significance of the neurochemical diversity of renal afferent and efferent nerves represents a critical gap in our understanding of neural control of kidney function. Our central hypothesis is that efferent and afferent nerves with distinct neurochemical signatures differentially control renal functions through their association with distinct renal structures. We will use state-of- the-art neurophysiological and neuroanatomical approaches to generate an integrated functional and structural map of neural control in the mouse kidney. We will also initiate translation of these finding to the human kidney through comprehensive neuroanatomical analysis. In Specific Aim 1 will test the hypothesis that neurochemically distinct renal nerves differentially control renal function. In Specific Aim 2 we will test the hypothesis that neurochemically distinct renal nerves are associated with distinct structures in the kidney. Finally, in Specific Aim 3 we will define the structural neurobiology of renal efferent and afferent nerves, and their relationship to vascular, tubular and renal pelvis anatomy in the human kidney.