Resiniferatoxin provides further evidence for a role of capsaicin-sensitive sensory neurons in the control of the kidney function.

Neonatal capsaicin treatment has been reported to impair the excretory function of the kidney in the rat. The present study evaluated the effect on urine excretion of the neurotoxin resiniferatoxin, an extremely potent structural analogue of capsaicin. Neonatal resiniferatoxin treatment (30 micrograms/kg) markedly reduced diuresis, natriuresis and kaliuresis in adult rats, in response to intragastric saline or water load and to furosemide administration, as well as in basal conditions. The effect of resiniferatoxin was more pronounced and long-lasting than that observed in previous studies following neonatal capsaicin treatment (50 mg/kg). On the other hand, administration of resiniferatoxin in adult rats did not affect urine excretion, suggesting that afferent fibers resistant to the neurotoxin treatment during adulthood, might be involved in the effect. The results of the present study are in keeping with the hypothesis that neuropeptides-containing capsaicin-sensitive sensory neurons might be involved in the physiological modulation of the kidney function.