Paraurethral striated muscular structures and pelvic floor muscles contribute to resting urethral closure pressure in rats

Introduction and hypothesis: We investigated physiological functions of the extraordinary muscular structure in the paraurethral area with pelvic floor muscle and the impact of these muscular structures on the resting maximal urethral closure pressure (MUCP) in rats. Methods: Sixteen female Wister rats were divided into four groups: Groups I and II rats received 5 and 2.5 IU botulinum toxin A (BoNT-A), respectively, injected into the bilateral paraurethral striated muscles. Group III rats received 2.5 IU BoNT-A injected into the bilateral pelvic floor muscles, and group IV rats received 2.5 IU BoNT-A injected into the unilateral pelvic floor muscles. Measurements of MUCP were made at different time points after BoNT-A injection. Results All groups showed a rapid reduction in average MUCP by 70-80 % after BoNT-A injection, regardless of injection site or side. Conclusions: Paraurethral striated muscular structures and the pelvic floor muscles possess the function of maintaining resting MUCP in rats.