Suppression of bladder overactivity by activation of somatic afferent nerves in the foot

To investigate the possibility of suppressing bladder overactivity by electrical activation of somatic afferent nerves in the foot.

Cats with an intact spinal cord were studied under α-chloralose anaesthesia. Bladder pressure was recorded via a urethral catheter. Foot stimulation was applied via surface pad electrodes attached to the skin of the front or hind foot.

Reflex micturition was inhibited by electrical stimulation of the hind foot at either low (5 Hz) or high (20 Hz) frequencies, but stimulation of the front foot was ineffective. The mean (sem) bladder capacity during a saline infusion cystometrogram (CMG) was significantly (P < 0.05) increased to 153.2 (18.2)% and 136.9 (14.3)% of the control bladder capacity by stimulation at frequencies of 5 Hz and 20 Hz, respectively. Intravesical infusion of 0.25% acetic acid (AA) induced bladder overactivity and reduced bladder capacity to 20.3 (8.9)% of the control capacity measured during saline infusion. Foot stimulation inhibited the AA-induced bladder overactivity recorded under isovolumetric conditions, and significantly (P < 0.05) increased bladder capacity during AA infusion. However, it only restored the small bladder capacity caused by AA irritation to 40-50% of the control bladder capacity measured during saline infusion. The effect of foot stimulation did not persist after termination of stimulation during repeated CMG tests.

This study shows the potential of noninvasive transcutaneous electrical stimulation of somatic nerves in the foot to inhibit reflex bladder activity and treat overactive bladder symptoms.