Efficacy of different spinal nerve roots for neuromodulation of micturition reflex in rats
Electrical stimulation of peripheral nerves controlling the bladder offers an alternative, non-destructive medical treatment for urinary incontinence and retention. The aim of the present study was to identify the most efficient sensory and motor spinal nerve roots involved in micturition reflex.
Twelve SD rats underwent unilateral L5-S2 dorsal roots (DRTs) and ventral roots (VRTs) electrically stimulation and the bladder reflex contractions (BRCs) were recorded under isovolumetric condition. Pseudorabies virus (PRV) were injected into the bladder detrusor in six rats. L5-S2 spinal cords and dorsal root ganglions (DRGs) were harvested for immunohistochemistry study.
Repeated stimulation of L6 and S1 DRTs not only abolished BRC but also induced a post-stimulation inhibitory effect, whereas repeated stimulation of L5 and S2 DRTs had no influence. Only L6 VRT directly caused bladder contraction when the VRTs of L5-S2 were stimulated in sequence. PRV retrograde tracing demonstrated that the sacral parasympathetic nucleus (SPN) of L6 segment was more strongly PRV-positive compared with the other segments. On the other hand, the S1 DRG was found to have the highest density of PRV-positive neurons.
In conclusion, various afferent and efferent nerves innervate the bladder and are involved in micturition reflex, but the L6 VRT could be the most efficient in producing detrusor muscle contraction, and the S1 DRT could have the superiority of inhibiting micturition reflex.
Funding: National Natural Science Foundation of China (No. 81370862).