Evaluation of the Potential Inhibitory Effects of Medications for Detrusor Overactivity on Platelet-Activating Factor (PAF)-Induced Mechanical Activity in Guinea Pig Bladder Smooth Muscle

Abstract

This study aimed to determine whether currently available medications for detrusor overactivity (DO) can inhibit the platelet-activating factor (PAF)-induced increase in the mechanical activity of the urinary bladder smooth muscle (UBSM) in guinea pigs. Ten clinically used DO drugs—oxybutynin, tolterodine, fesoterodine, propiverine, propantheline, solifenacin, imidafenacin, flavoxate, urapidil, and clenbuterol—were tested at a concentration of 10 μM, exceeding typical therapeutic plasma levels. Among these, oxybutynin exerted the most pronounced inhibitory effect, reducing the PAF (1 μM)-induced increase in basal tone by approximately 60%. Furthermore, oxybutynin (10 μM) also decreased 60 mM KCl-induced contractions by a similar extent and nearly abolished acetylcholine (ACh, 10 μM)-induced contractions. These findings suggest that oxybutynin suppresses PAF-induced UBSM hyperactivity through a mechanism distinct from its anticholinergic effect, likely mediated by blockade of voltage-dependent Ca²⁺ channels (VDCCs).