Urodynamic Effects of Intravesical Resiniferatoxin and Capsaicin in Conscious Rats With and Without Outflow Obstruction

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Abstract
The urodynamic effects of intravesical resiniferatoxin and capsaicin were investigated in rats. Continuous cystometry was performed in conscious, female Sprague-Dawley rats with and without outflow obstruction. Intravesical instillation of resiniferatoxin facilitated micturition. The potency of the drug was approximately 1,000 times higher than that of capsaicin. Repeated instillations of resiniferatoxin for 6 consecutive days caused desensitization to resiniferatoxin. This was not found with repeated instillations of capsaicin. Capsaicin was also effective in rats with bladder hypertrophy, while resiniferatoxin was not. The findings suggest that resiniferatoxin can induce desensitization of vanilloid receptor-mediated release of tachykinins in the rat urinary bladder and that intravesical resiniferatoxin would be an interesting alternative to intravesical capsaicin in the treatment of selected cases of bladder hypersensitivity/hyperactivity.