In-vivo whole bladder response to anticholinergic and musculotropic agents in spinal cord injured rats

The purpose of this study was to compare the effect on urodynamic parameters of anticholinergic and musculotropic agents in sham injured and spinal cord injured (SCI) rats. A standard rat SCI model induced by impact trauma was employed. Cystometrograms were performed under urethane anesthesia four weeks after SCI. Bladder capacity and voiding pressure were determined at the point of micturition monitored urodynamically and visually. The effect of oxybutynin chloride (0.01-0.1 mg/kg), propantheline bromide (0.05-0.5 mg/kg) and flavoxate hydrochloride (0.1-1.0 mg/kg) were assessed independently in sham injured and SCI rats (n = 10 in each group). Bladder capacities were 0.6 +/- 0.2 and 7.1 +/- 1.6 ml in sham and SCI rats (p < 0.01), respectively. Maximal filling pressure was 17.5 +/- 5 mmHg in sham and 25 +/- 5 mmHg in SCI rats (p < 0.05). Bladder capacity increased with all three medications. Administration of oxybutynin, propantheline and flavoxate in sham rats resulted in bladder capacities of 0.88 +/- 0.3, 0.71 +/- 0.3 and 0.8 +/- 0.2 ml, respectively (p < 0.01). In SCI rats, these drugs resulted in bladder capacities of 9.8 +/- 1.1, 7.9 +/- 1.3 and 8.8 +/- 2.0 ml, respectively (p < 0.01). No significant change in maximum filling pressure occurred. We conclude that anticholinergic and musculotropic agents caused a similar increase in bladder capacity in both sham and SCI rats. Oxybutynin enhanced bladder capacity more than propantheline or flavoxate.