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Transient receptor potential vanilloid type 1 channels act as mechanoreceptors and cause substance P release and sensory activation in rat kidneys

¹Division of Chest Medicine, Department of Internal Medicine, Kaohsiung Armed Forces General Hospital, Kaohsiung; ²Department of Urology, Cardinal Tien Hospital, Hsintien; ³Division of Nephrology, Department of Internal Medicine, Kaohsiung Armed Forces General Hospital, Kaohsiung; and ⁴School of Medicine, Fu-Jen Catholic University, Hsinchuang, Taiwan

Submitted 5 July 2007 ; accepted in final form 9 November 2007

Stimulation of capsaicin receptors results in an increase in afferent renal nerve activity (ARNA), but it is unclear how capsaicin contributes to sensory activation intrarenally. Here, we studied the relationships between capsaicin receptor activation, substance P (SP) release, and the sensory response in the rat renal pelvis. Immunoblots showed that one of the capsaicin receptors, transient receptor potential vanilloid type 1 channel (TRPV1), was found in various renal tissues and was especially abundant in the renal pelvis, where most sensory nerve fibers originate. Interestingly, immunolabeling showed colocalization of TRPV1, SP, and the panneuronal marker PGP9.5 in the renal pelvis. Electrophysiological recordings showed that SP and capsaicin activated the same mechanosensitive ARNA in a single-unit preparation. Intrapelvic administration of capsaicin or a specific TRPV1 agonist, resiniferatoxin, resulted in a dose-dependent increase in multi-unit ARNA and SP release, and these effects were blocked by the TRVP1 blocker capsazepine. Inhibition of the SP receptor by L-703,606 largely prevented capsaicin- or resiniferatoxin-induced ARNA. Capsazepine also prevented intrapelvic pressure (IPP)-dependent ARNA activation and contralateral diuresis/natriuresis in the renorenal reflex at an IPP of 20 mmHg, but had no effect at an IPP of 50 mmHg. These data indicate that TRPV1, a low-pressure baroreceptor, is present in the renal pelvis and exclusively regulates neuropeptide release from primary renal afferent C-fibers in response to mechanostimulation.

neurokinin-1 receptor; renorenal reflex; capsaicin receptor; intrapelvic pressure

This article has been cited by other articles:

				T. Ditting, R. Veelken, and K. F. Hilgers Transient Receptor Potential Vanilloid Type 1 Receptors in Hypertensive Renal Damage: A Promising Therapeutic Target? Hypertension, August 1, 2008; 52(2): 213 - 214. [Full Text] [PDF]