Frequency-dependent inhibition of bladder function by saphenous nerve stimulation in anesthetized rats.

AIMS

Percutaneous tibial nerve stimulation (PTNS) is an effective neuromodulation therapy for treating overactive bladder (OAB). The therapeutic effects are achieved by repeatedly applying electrical stimulation through a percutaneous needle electrode that is used to target the tibial nerve (TN). Anatomical studies indicate there can be multiple saphenous nerve (SAFN) branches located near the site of electrical stimulation, and therefore we investigated the possibility of evoking a bladder-inhibitory reflex by electrically activating the SAFN.

MATERIALS AND METHODS

Acute experiments were conducted in 26 urethane-anesthetized rats. Changes in bladder contraction rate (BCR) and bladder capacity were measured in response to 10-min SAFN stimulation trials. Electrical pulses were applied at 25 µA and at stimulation frequencies between 2 Hz and 50 Hz.

RESULTS

We report that SAFN stimulation at 20 Hz was most effective at reflexively decreasing the BCR (53.8 ± 5.4% from baseline) and also increasing the bladder capacity (145.8 ± 43.5% from baseline). In contrast, SAFN stimulation at other frequencies yielded inconsistent changes in bladder function. Carry-over effects were minimized by randomizing the sequence of SAFN stimulation trials and also by allowing the bladder to return to the baseline conditions.

CONCLUSIONS

With notable changes in both the BCR and bladder capacity, our findings provide evidence of a novel bladder-inhibitory reflex in anesthetized rats that is mediated by the SAFN. Further work is needed to determine the clinical relevance of this neural pathway.