Functional roles of transient receptor potential melastatin 8 (TRPM8) channels in the cold stress-induced detrusor overactivity pathways in conscious rats

Aims We determined if transient receptor potential melastatin 8 (TRPM8) channels are involved in the detrusor overactivity induced by menthol, or exposure to low temperature (LT). Methods Two days prior to cystometric investigation, the bladders of 10-week-old Sprague-Dawley rats were cannulated to measure bladder pressure. After a 20min baseline cystometry period, the TRPM8 channel antagonist, N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)piperazine-1-carboxamide (BCTC), or vehicle, was administered through a jugular vein catheter (n=6). A 90% menthol solution was sprayed onto bare leg skin once every 5min for 20min, and then cystometric measurements were repeated. After a 30-min recovery period, the rats were intravenously administered 0.1 mu mol/kg BCTC. Five minutes later, they were again sprayed and cystometry recorded. In separate experiments, cannulated rats were intravenously administered 0.001, 0.01, or 0.1 mu mol/kg BCTC (n=6 each dose). Five minutes later, they were exposed to LT (4 +/- 2 degrees C) for 20min of cystometry. Results Menthol spray decreased voiding interval, micturition volume, and bladder capacity in the BCTC-free rats. However after BCTC administration, these effects were prevented. Exposure to LT elicited detrusor overactivity that caused decreased voiding interval, micturition volume, and bladder capacity. However, at 0.01 and 0.1 mu mol/kg, BCTC inhibited this cold stress-induced detrusor overactivity. Conclusions Since the TRPM8 channel agonist, BCTC, inhibited detrusor overactivity in rats sprayed with the TRPM8 channel agonist, menthol, and the drug also inhibited cold stress-induced detrusor overactivity, we conclude that TRPM8 channels mediate, at least partially, detrusor overactivity elicited by exposure to LT. Neurourol. Urodynam. 32: 500-504, 2013. (c) 2012 Wiley Periodicals, Inc.