The frequency spectrum of bladder non-voiding activity as a trigger-event for conditional stimulation: Closed-loop inhibition of bladder contractions in rats

Aims: To test the hypothesis that the frequency of bladder non-voiding contractions (NVCs) can be used as a trigger event for closed-loop conditional inhibition of detrusor contractions via tibial nerve (TN) or dorsal penile nerve (DPN) stimulation. Methods: In urethane anaesthetized male Wistar rats, the bladder was filled continuously with saline to evoke contractions. To test the plausibility of conditional inhibition via the TN, electrical stimulation was switched on manually when the pressure increased above a threshold of 10 cmH20 above the baseline. For testing conditional stimulation via the DPN, the pressure signal was continuously stored and a baseline threshold, the area under the curve (AUC) of the amplitude spectrum in the 0.2–20 Hz range of a 5 s window at the beginning of filling was calculated. When the AUC of subsequent pressure windows superseded the baseline threshold, the DPN was automatically stimulated. Results: TN stimulation failed to inhibit evoked voiding contractions. The NVC frequency spectrum based DPN stimulation successfully inhibited 70% of the evoked contractions and resulted in a 45% increase in bladder capacity (BC). Conclusions: While, conditional TN stimulation failed to suppress bladder contractions, DPN stimulation, automatically triggered by an increased frequency of bladder non-voiding activity, resulted in bladder inhibition, and a consequential increase in BC. This study demonstrates the plausibility of using the frequency of NVCs as a trigger event for conditional inhibition of detrusor contractions.

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