Experimental study of the effect of capsaicin on the urinary bladder function in rats

In order to investigate the effect of capsaicin (CAP) on the urinary bladder function, an in vivo whole bladder study was undertaken in 25 adult healthy Wistar rats. CAP of various concentrations was instilled into the urinary bladder, and intravesical pressure, detrusor contraction and micturition status were recorded; then the trigone of the bladder was cut off and prepared for peroxidase-antiperoxidase (PAP) immunohistochemical investigation. The changes on the distribution of Substance P (SP) in control and experimental groups were compared. The results showed that the intravesical application of CAP caused a significant change in the urinary bladder function. At a low concentration of CAP there was a slight increase of maximal detrusor pressure, but at a high concentration of CAP the maximal intravesical pressure was significantly decreased and associated with urinary retention and urinary incontinence. PAP sustaining had shown a depletion of SP in CAP-treated urinary bladder in rats, and this depletion was more significant at high concentrations of CAP. Because this depletion could block C-fiber transmission, detrusor function entered, from primary excitation phase, a late inhibitory phase. This suggests that a local application of CAP into urinary bladder could be used in the treatment of neurogenic bladder (detrusor hyperreflexia) to relieve frequency, urgency, incontinence and improve renal function.