Effects of periurethral neuromuscular electrical stimulation on the voiding frequency in rats

Introduction and hypothesis: This study aims to test the hypothesis that a urethra-to-bladder inhibitory pathway exists through which periurethral neuromuscular electrical stimulation (NMES) inhibits overactive bladder contractions in rats. Methods: Bladder overactivity was induced in 22 female Sprague Dawley rats by injection of ketamine/xylazine/acepromizine (K/X/A). A bipolar electrode was placed surgically in the periurethral region to deliver NMES. Intravesical pressure, bladder inter-contraction interval (ICI) and voided volume (VV) were monitored while the bladder was continuously infused with saline. Results: K/X/A induced more frequent bladder contractions (ICI=48.6±20.1 s, before cutting the pubo-symphasis) compared to a 10-min ICI induced by urethane. NMES significantly increased ICI (63.1±31.3 s before vs. 97.2± 42.9 s after NMES, p<0.001) and VV (0.063=0.041 ml before vs. 0.088=0.044 ml after NMES, p<0.02). Conclusions: Injection of K/X/A may potentially be used as a model of bladder overactivity. NMES inhibits bladder contractions in rats with bladder overactivity, which supports the existence of a urethra-to-bladder inhibitory pathway.