Reflex bladder activation via pudendal nerve and intraurethral stimulation depends on stimulation pattern and location

Pudendal nerve (PN) stimulation and intraurethral stimulation via a catheter have been demonstrated previously to trigger reflex bladder contractions for 20–40 Hz and 2 & 20 Hz continuous stimuli, respectively. However, thorough studies of the stimulation parameter space and optimal urethral locations are required for translation to clinical feasibility studies for potential neural prostheses. Stimulation-evoked bladder activation was evaluated in fourteen male cats via PN stimulation or intraurethral stimulation before and after spinal transection. In all testing scenarios, the use of pulse bursting led to a greater evoked bladder pressure than with single-pulse continuous waveforms. PN stimulation evoked contractions with 1 Hz and 33 Hz stimuli before spinalization in eight cats. Post-spinalization testing in four cats only elicited excitation for 33 Hz stimuli. For PN stimulation, spinalization eliminated the excitability of low frequency stimulation. Intraurethral stimulation in the proximal and prostatic urethra (2 Hz and 33 Hz range stimuli) and the distal urethra (33 Hz range stimuli) evoked contractions in six cats before spinalization. After spinalization, intraurethral testing in five cats only evoked contractions in the distal and prostatic urethra using 33 Hz range stimuli. For intraurethral stimulation, spinalization eliminated both proximal and low frequency responses. This research improves the knowledge base of several main factors involved in the development of neuroprostheses for bladder control - optimal stimulation paradigms and the understanding of lower urinary tract neurophysiology.