Bilateral pudendal afferent stimulation improves bladder emptying in rats with urinary retention

Abstract

Objective: To determine whether bilateral electrical stimulation (BiES) of the transected pudendal sensory nerves could further enhance the voiding efficiency beyond that produced by unilateral electrical stimulation (UniES) of transected pudendal afferents in rats with urinary retention.

Materials and methods: The efficiency of bladder emptying with either UniES or BiES of pudendal nerve afferents was measured after acute bilateral transection of the sensory branch of the pudendal nerve. The effects of UniES and BiES on voiding in a partially denervated bladder and acute spinal transection, respectively, were determined.

Results: The voiding efficiency (VE) was reduced from 69 to 22% after bilateral transection of the sensory branch of the pudendal nerve. UniES or BiES increased the VE to 49-62%. Although in most instances BiES consistently generated more efficient bladder emptying than did UniES, these differences were not significant. Both UniES and BiES increased VE after unilateral pelvic nerve transection, demonstrating efficacy in a partially denervated bladder. The enhancement of VE by either UniES or BiES was preserved after acute T(9)-T(10), demonstrating the spinal origin of this augmenting reflex.

Conclusions: The results of the present study are consistent with an essential role for pudendal sensory feedback in efficient bladder emptying, and unilateral and bilateral electrical activation of pudendal nerve afferents are equally efficient in improving bladder emptying in an animal model of urinary retention. This could provide an approach to improve bladder emptying in patients with non-obstructive urinary retention.

FIG. 1

Examples of the effects of UniES or BiES of the proximal end of the transected sensory branch of the pudendal nerves on isovolumetric reflex bladder contractions. (A) Isovolumetric bladder contractions without concomitant stimulation. (B)–(D) Either UniES or BiES was delivered during every other bladder contraction. The horizontal bars indicate 30 s of UniES or BiES, which began when the bladder pressure exceeded 50 cmH₂O. The stimulus trains were all at 2 Hz with various current amplitudes and a 0.05 ms pulse width.

FIG. 2

Effects of UniES and BiES of the proximal end of the transected sensory branch of the pudendal nerve on bladder pressure and EUS EMG during continuous bladder infusion. Traces on the right are expansions of the section of the traces on the left in brackets. The BP is the duration of EUS EMG bursting period. (A) Bladder pressure and EUS EMG before any nerve transection; (B) bladder pressure and EUS EMG after BST; (C) bladder pressure and EUS EMG after BST with UniES (20 Hz, 0.05 mA); (D) bladder pressure and EUS EMG after BST with BiES (20 Hz, 0.05 mA). UniES or BiES was delivered when the bladder pressure exceeded 20 cmH₂O and stopped when the pressure returned to below this threshold, as indicated by the horizontal bars.

FIG. 3

Effects of UniES and BiES of the proximal end of the transected sensory branch of the pudendal nerve on bladder pressure (A) and VE (B) after successive pelvic nerve transections (Nx). UniES or BiES (20 Hz, 0.05 mA) was delivered when the bladder pressure exceeded 15 cmH₂O and stopped when the pressure returned to below this threshold, as indicated by the horizontal bars in A. Each bar in B represents the mean ± SD (n = 6 rats). #, significant difference (P < 0.05) compared with after BST; *, significant difference (P < 0.05) compared with after unilateral pelvic Nx. BiNx, bilateral pelvic nerve transection.

FIG. 4

Effects of UniES and BiES of the proximal end of the transected sensory branch of the pudendal nerve on bladder pressure (A) and VE (B) after acute T₉–T₁₀ SCT. UniES or BiES (20 Hz, 0.05 mA) was delivered when the bladder pressure exceeded 20 cmH₂O and stopped when the pressure returned to below this threshold, as indicated by the horizontal bars in A. Each bar in B represents the mean ± SD (n = 6 trails across three rats). #, significant difference (P < 0.05) compared with after BST; *, significant difference (P < 0.05) between post-acute SCT and trials in which stimulation was applied.