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lüll Do distinct populations of dorsal root ganglion neurons account for the sensory peptidergic innervation of the kidney?Ditting T; Tiegs G; Rodionova K; Reeh PW; Neuhuber W; Freisinger W; Veelken RAm J Physiol Renal Physiol 2009[Nov]; 297 (5): F1427-34Peptidergic afferent renal nerves (PARN) have been linked to kidney damage in hypertension and nephritis. Neither the receptors nor the signals controlling local release of neurokinines [calcitonin gene-related peptide (CGRP) and substance P (SP)] and signal transmission to the brain are well-understood. We tested the hypothesis that PARN, compared with nonrenal afferents (Non-RN), are more sensitive to acidic stimulation via transient receptor potential vanilloid type 1 (TRPV1) channels and exhibit a distinctive firing pattern. PARN were distinguished from Non-RN by fluorescent labeling (DiI) and studied by in vitro patch-clamp techniques in dorsal root ganglion neurons (DRG; T11-L2). Acid-induced currents or firing due to current injection or acidic superfusion were studied in 252 neurons, harvested from 12 Sprague-Dawley rats. PARN showed higher acid-induced currents than Non-RN (transient: 15.9 +/- 5.1 vs. 0.4 +/- 0.2* pA/pF at pH 6; sustained: 20.0 +/- 4.5 vs. 6.2 +/- 1.2* pA/pF at pH 5; *P < 0.05). The TRPV1 antagonist capsazepine inhibited sustained, amiloride-transient currents. Forty-eight percent of PARN were classified as tonic neurons (TN = sustained firing during current injection), and 52% were phasic (PN = transient firing). Non-RN were rarely tonic (15%), but more frequently phasic (85%), than PARN (P < 0.001). TN were more frequently acid-sensitive than PN (50-70 vs. 2-20%, P < 0.01). Furthermore, renal PN were more frequently acid-sensitive than nonrenal PN (20 vs. 2%, P < 0.01). Confocal microscopy revealed innervation of renal vessels, tubules, and glomeruli by CGRP- and partly SP-positive fibers coexpressing TRPV1. Our data show that PARN are represented by a very distinct population of small-to-medium sized DRG neurons exhibiting more frequently tonic firing and TRPV1-mediated acid sensitivity. These very distinct DRG neurons might play a pivotal role in renal physiology and disease.|Acid Sensing Ion Channels[MESH]|Acids/metabolism[MESH]|Animals[MESH]|Cells, Cultured[MESH]|Electrophysiology[MESH]|Ganglia, Spinal/cytology/*physiology[MESH]|Immunohistochemistry[MESH]|Kidney Cortex/innervation/physiology[MESH]|Kidney/*innervation[MESH]|Male[MESH]|Membrane Potentials/physiology[MESH]|Microscopy, Confocal[MESH]|Nerve Fibers/physiology[MESH]|Nerve Tissue Proteins/physiology[MESH]|Neuropeptides/*physiology[MESH]|Patch-Clamp Techniques[MESH]|Rats[MESH]|Rats, Sprague-Dawley[MESH]|Sensory Receptor Cells/*physiology[MESH]|Sodium Channels/physiology[MESH]|TRPV Cation Channels/physiology[MESH] |