Pathways and parameters of sacral neuromodulation in rats

Area of Science:

• Neuroscience
• Urology
• Biomedical Engineering

Background:

• The stimulation paradigm for sacral neuromodulation (SNM) has remained largely unchanged.
• Understanding the relationship between stimulation parameters and nerve activation is crucial for optimizing SNM therapy.
• Previous studies have not fully elucidated the effects of varying stimulation amplitudes and locations on bladder function.

Purpose of the Study:

• To determine if stimulation-induced increases in rat bladder capacity correlate with the proportion of sensory pudendal (PudS) neurons at stimulated locations (L6, S1).
• To investigate the effects of different stimulation amplitudes on bladder capacity and voiding efficiency.
• To compare acute high-amplitude stimulation effects in animal models with chronic low-amplitude clinical SNM.

Main Methods:

• Rats (CD, obese-prone, obese-resistant) underwent acute electrical stimulation at L6 or S1.
• Cystometric studies were performed at varying stimulation amplitudes (1-6 times motor threshold [Tm]).
• Pudendal nerve activation and bladder capacity were measured.

Main Results:

• Acute low-amplitude stimulation (1-1.5 Tm) did not increase bladder capacity, irrespective of stimulation location.
• S1 infrequently contributed nerve fibers to the PudS nerve.
• Stimulation at higher amplitudes (1-6 Tm) increased bladder capacity and decreased voiding efficiency, mirroring PudS nerve stimulation effects.

Conclusions:

• Acute low-amplitude SNM does not increase bladder capacity in rats.
• Increased stimulation amplitude correlates with enhanced bladder capacity and PudS nerve recruitment.
• The mechanistic relationship between high-amplitude acute animal stimulation and chronic low-amplitude clinical SNM requires further investigation.