Bladder inhibition or excitation by electrical perianal stimulation in a cat model of chronic spinal cord injury

OBJECTIVE To test the hypothesis that perianal electrical stimulation (PES) in chronic spinal cord-injured (SCI) cats could induce frequency-dependent inhibitory or excitatory reflex bladder responses. MATERIALS AND METHODS The experiments were conducted ≥4–5 weeks after spinal cord transection at the T9-T10 level. PES was applied via a pair of hook electrodes to the perianal skin area in three awake female cats with chronic SCI. A double-lumen balloon catheter was inserted through the urethra into the bladder to monitor bladder pressure and infuse saline (2–4 mL/min). RESULTS Under isovolumetric conditions PES at 3–10 Hz significantly inhibited large-amplitude reflex bladder activity induced by bladder distension above the micturition volume threshold. However, PES at 20–50 Hz induced large-amplitude bladder contractions when the bladder volume was below the micturition volume threshold. Inhibitory PES (7 Hz) significantly increased the mean (sem) bladder capacity by 40 (10)% when it was applied continuously during cystometrography. The optimum excitatory PES (30 Hz) induced large-amplitude (>25 cmH2O), long-duration (>20 s) bladder contractions at a wide range of bladder volumes (10–90% of bladder capacity). CONCLUSIONS This study showed that activation of pudendal afferent fibres by PES could induce frequency-dependent reflex bladder responses in awake cats with chronic SCI, indicating that a possible noninvasive treatment based on PES could be developed to restore both continence and micturition function for patients with SCI.