URODYNAMIC EFFECTS OF INTRAVESICAL RESINIFERATOXIN AND CAPSAICIN IN CONSCIOUS RATS WITH AND WITHOUT OUTFLOW OBSTRUCTION

Purpose: The urodynamic effects of intravesical resiniferatoxin and ca psaicin were investigated in rats. Materials and Methods: Continuous c ystometry was performed in conscious, female Sprague-Dawley rats with and without outflow obstruction. Results: Intravesical instillation of resiniferatoxin facilitated micturition. The potency of the drug was approximately 1,000 times higher than that of capsaicin. Repeated inst illations of resiniferatoxin for 6 consecutive days caused desensitiza tion to resiniferatoxin. This was not found with repeated instillation s of capsaicin. Capsaicin was also effective in rats with bladder hype rtrophy, while resiniferatoxin was not. Conclusions: The findings sugg est that resiniferatoxin can induce desensitization of vanilloid recep tor-mediated release of tachykinins in the rat urinary bladder and tha t intravesical resiniferatoxin would be an interesting alternative to intravesical capsaicin in the treatment of selected cases of bladder h ypersensitivity/hyperactivity.