Evidence of vagus nerve sprouting to innervate the urinary bladder and clitoris in a canine model of lower motoneuron lesioned bladder

Authors

Mary F. Barbe, Sandra Gomez-Amaya, Alan S. Braverman, Justin M. Brown, Neil S. Lamarre, Vicky S. Massicotte, Jennifer K.S. Lewis, Stephen R. Dachert and Michael R. Ruggieri Sr.

Abstract

Aims
Complete spinal cord injury does not block perceptual responses or inferior solitary nucleus activation after genital self-stimulation, even though the vagus is not thought to innervate pelvic structures. We tested if vagus nerve endings sprout after bladder decentralization to innervate genitourinary structures in canines with decentralized bladders.

Methods
Four reinnervation surgeries were performed in female hounds: bilateral genitofemoral nerve transfer to pelvic nerve with vesicostomy (GNF-V) or without (GFN-NV); and left femoral nerve transfer (FNT-V and FNT-NV). After 8 months, retrograde dyes were injected into genitourinary structures. Three weeks later, at euthanasia, reinnervation was evaluated as increased detrusor pressure induced by functional electrical stimulation (FES). Controls included un-operated, sham-operated, and decentralized animals.

Results
Increased detrusor pressure was seen in 8/12 GFNT-V, 4/5 GFNT-NV, 5/5 FNT-V, and 4/5 FNT-NV animals after FES, but not decentralized controls. Lumbar cord segments contained cells labeled from the bladder in all nerve transfer animals with FES-induced increased detrusor pressure. Nodose ganglia cells labeled from the bladder were observed in 5/7 nerve transfer animals (1/2 GNT-NV; 4/5 FNT-V), and from the clitoris were in 6/7 nerve transfer animals (2/2 GFNT-NV; 4/5 FNT-V). Dorsal motor nucleus vagus cells labeled from the bladder were observed in 3/5 nerve transfer animals (1/2 GFNT-NV; 2/3 FNT-V), and from the clitoris in 4/5 nerve transfer animals (1/2 GFNT-NV; 3/3 FNT-V). Controls lacked this labeling.

Conclusions
Evidence of vagal nerve sprouting to the bladder and clitoris was observed in canines with lower motoneuron lesioned bladders