Characterization of bilateral, pudendal nerve-evoked, urethral rhabdosphincter contractions in anesthetized cats
Pudendal (PUD) efferent activity contracts urethral rhabdosphincters to resist urine leakage. This study evaluates the potential for PUD nerve stimulation to provide benefit for urinary incontinence. Acute responses of the urethral rhabdosphincter to modulation of current amplitude, pulse duration (PD), and frequency of stimulation were examined. Urethral pressure was measured using a microtip catheter in chloralose-anesthetized, male cats with or without acute spinalization at T10. Stimulation was applied from an external pulse generator coupled to cuff electrodes placed around left and right PUD nerves in the ischiorectal fossa, central to its branching. Bladder pressure clamp techniques were used for testing effects of stimulation on time and rate of leakage during PUD stimulation. Single pulses (0.1 ms) produced single transient increases in urethral pressure that peaked at 50 ms and diminished to 50% of peak at 90 ms. Threshold current was 88 ± 30μA with maximal responses occurring with 50% increases in current. Peak pressures increased with increasing PDs between 40–180μs. Summation, tetany, peak pressures, and fatigue of responses to increasing stimulation frequencies during 2 min periods of stimulation are described. Stimulation under pressures that are typical during bladder filling or during bladder contractions (30–40 cm H
