Transcutaneous Neuromodulation Promotes Functional Regeneration of the External Urethral Sphincter Neural Circuitry in Two Models of Nerve Lesion in Female Rats.

Abstract

Objective: This study investigated the effect of transcutaneous electrical stimulation of the dorsal nerve of the clitoris (DNC-TENS) on the functional recovery of the neural circuitry of the external urethral sphincter (EUS) neural circuitry in two models of childbirth trauma in rats: vaginal distension (VD) and injury of the motor branch of the pudendal nerve (MBPN).

Materials and methods: In total, 42 Wistar adult female rats were used. Rats underwent sham VD (SH-VD), VD with sham DNC-TENS (VD SH-TENS) or VD with DNC-TENS, bilateral crush of MBPN crush injury (MBPNC) with sham DNC-TENS, or MBPNC with DNC-TENS. Stimulation was delivered to the dorsal region of the clitoral sheath, immediately and on days 2 and 4 after VD or MBPNC. The outcome parameters were EUS electromyograms (EMGs, amplitude and frequency) and cystometrograms (CMGs). Animals were evaluated at seven and 14 days after VD or SH-VD and at day 9 after the nerve crush.

Results: In SH-VD animals, the EUS EMG activity increased concurrently with bladder contraction. Tonic and bursting responses also were observed. VD significantly impaired EUS and CMG characteristics in the first week postlesion; in the VD SH-TENS group, the bursting EMG response was abolished; the amplitude of tonic activity decreased (p < 0.0001), and the duration of bladder contraction decreased. DNC-TENS facilitated recovery of bursting and tonic EUS EMG activity after VD (p < 0.0001). As with VD, MBPNC abolished EUS bursting activity and decreased (∼80%) tonic activity. TENS significantly improved EMG and CMG parameters.

Conclusions: VD and MBPNC significantly impair EUS EMG activity. DNC-TENS facilitates functional recovery of the EUS neural circuitry by promoting neuroregeneration and increases bladder compliance. Further studies are required to determine whether DNC-TENS is an effective noninvasive neuromodulation therapy to alleviate or prevent symptoms of stress urinary incontinence associated with childbirth trauma in women.