Bladder activation by selective stimulation of pudendal nerve afferents in the cat

Bladder contractions evoked by pudendal nerve stimulation in both spinal intact and spinal transected cats support the possibility of restoring urinary function in persons with chronic spinal cord injury (SCI). However, electrically evoked bladder responses in persons with SCI were limited to transient contractions at relatively low pressures. This prompted the present study, which presents a detailed quantification of the responses evoked by selective stimulation of individual branches of the pudendal nerve at different stimulation frequencies. In spinal intact cats anesthetized with α-chloralose, selective frequency-dependent electrical activation of the sensory (2 Hz ≤ f ≤ 50 Hz), cranial sensory (f ≤ 5 Hz), dorsal genital (f ≥ 20 Hz) and rectal perineal (f ≤ 10 Hz) branches of the pudendal nerve evoked sustained bladder contractions dependent on the stimulation frequency. Contractions evoked by selective electrical stimulation resulted in significant increases in voiding efficiency compared to bladder emptying by distension-evoked contractions (pANOVA < 0.05). Acute spinal transection abolished reflex bladder contractions evoked by low frequency stimulation of the cranial sensory or rectal perineal branches, whereas contractions evoked by high frequency stimulation of the dorsal genital branch remained intact. This study presents evidence for two distinct micturition pathways (spino-bulbo-spinal vs. spinal reflexes) activated by selective afferent pudendal nerve stimulation, the latter of which may be applied to restore bladder function in persons with SCI.