Post-Stimulation Inhibitory Effect on Reflex Bladder Activity Induced by Activation of Somatic Afferent Nerves in the Foot

Purpose: We determined whether transcutaneous electrical stimulation of somatic afferent nerves in the foot of cats would induce a post-stimulation increase in bladder capacity. Materials and Methods: In 12 alpha-chloralose anesthetized cats electrical stimulation (5 Hz) was applied to the skin of the hind foot for 2, 30-minute periods via dual pad electrodes attached on the plantar and dorsal surfaces (combination 1 and 2) or at 2 sites on the plantar surface (combination 1 and 3). The post-stimulation effect was examined by repeat cystometrogram after 30-minute stimulation. In the control group of 12 cats isovolumetric contractions were allowed to continue during each 30-minute period without stimulation. Results: Stimulation inhibited isovolumetric rhythmic bladder contractions. Bladder capacity was not increased after the first 30-minute foot stimulation via electrodes 1 and 2 but it was significantly increased a mean +/- SE of 47.5% +/- 2.9% after the second 30-minute stimulation via electrodes 1 and 3. After inducing the post-stimulation effect the foot stimulation applied during cystometrograms via electrodes 1 and 2 or 1 and 3 elicited a further increase in bladder capacity (mean 23.26% +/- 17.64% and 20.07% +/- 18.59%, respectively). Conclusions: Results show that the transcutaneous plantar electrical stimulation of somatic afferent nerves in the foot can induce a post-stimulation increase in bladder capacity, suggesting that an intermittent stimulation pattern rather than continuous stimulation might be effective as clinical application to treat overactive bladder symptoms.