Effect of Capsaicin on Detrusor Contractility-A Preliminary Study in Human and Rat Urinary Bladders

In order to understand how capsaicin affects detrusor contractility in rat and human urinary bladders, studies were undertaken. In the first study, capsaicin was administered intravesically to in vivo rats ; in the second, capsaicin was administered to in vitro rat bladdes; and in the third, capsaicin was administered to in vitro human bladders. Intravesical administration of low concentrations of capsaicin exerted an excitatory eddect on detrusor contractility in in vivo art urinary bladders, whereas intravesical administration of high concentrations of capsaicin had an inhibitory effect. In the isolatedwhole rat bladder study and in the in vitro rat bladder muscle strip study, a high concentration of at least imM was necessary for achieving an inhibitory effect under dither electrical or bethanechol stimulation. In the human bladder muscle strip study, the effect of capsaicin was more evident and dose-dependent. The results of these studies show that capsaicin releases neuropeptides in both rat and human bladders. It has been hypothesized that the release of these neuropeptides might facilitate normal detrusor contractility as well as reflexic micturition whereas a lack of these neuropeptides might inhibit normal detrusor contractility and reflexic micturition. A high concentration of capsaicin (more than 1 mM) was necessary in order to achieve this effect in both rat and human bldders.