Time course for urethral neuromuscular reestablishment and its facilitated recovery by transcutaneous neuromodulation after simulated birth trauma in rats

Abstract

The aims of the study were to determine the time-course of urinary incontinence recovery after vaginal distension (VD), elucidate the mechanisms of injury from VD leading to external urethral sphincter (EUS) dysfunction, and assess if transcutaneous electrical stimulation (TENS) of the dorsal nerve of the clitoris facilitates recovery of urinary continence after VD. Rats underwent 4-h VD, 4-h sham VD (SH-VD), VD plus 1-h DNC TENS, and VD plus 1-h sham TENS (SH-TENS). TENS or SH-TENS were applied immediately and at days 2 and 4 post-VD. Micturition behavior, urethral histochemistry and histology, EUS and nerve electrophysiology, and cystometrograms were evaluated. VD induced urine leakage and disrupted EUS fibers and nerve-conduction. Urine leakage disappeared 13 days post-VD. Structural and functional recovery of the EUS neuromuscular circuitry started by day 6 post-VD but did not fully recovered by day 11 post-VD. TENS significantly decreased the frequency of urine leakage post-VD (p<0.01). We conclude that rat urinary continence function after VD requires 2 weeks to recover, although urethra structure is not fully recovered. Treatment to facilitate neuroregeneration should be applied within one-week after damage. TENS facilitated urinary continence recovery after VD. This treatment may have potential to decrease postpartum urinary incontinence in women.