Electrical stimulation restores the specificity of sensory axon regeneration

[Guest guest]

Exp Neurol. 2005 Jul;194(1):221-9.

Electrical stimulation restores the specificity of sensory axon

regeneration.

Brushart TM, Jari R, Verge V, Rohde C, Gordon T.

Department of Orthopaedic Surgery, s Hopkins Medical

Institutions, 601 N. Caroline Street, Baltimore, MD 21287, USA.

Electrical stimulation at the time of nerve repair promotes

motoneurons to reinnervate appropriate pathways leading to muscle and

stimulates sensory neurons to regenerate. The present experiments

examine the effects of electrical stimulation on the specificity of

sensory axon regeneration. The unoperated rat femoral cutaneous

branch is served by 2-3 times more DRG neurons than is the muscle

branch. After transection and repair of the femoral trunk, equal

numbers of DRG neurons project to both branches. However, 1 h of

electrical stimulation restores the normal proportion of DRG neurons

reinnervating skin and muscle. To ask if the redistribution of

stimulated neurons results from enhanced specificity of target

reinnervation, we developed a new technique of sequential double

labeling. DRG neurons projecting to the femoral muscle branch were

prelabeled with Fluoro Gold 2 weeks before the nerve was transected

proximally and repaired with or without 1 h of 20-Hz electrical

stimulation. Three weeks after repair, the muscle nerve was labeled a

second time with Fluororuby. The percentage of regenerating neurons

that both originally served muscle and returned to muscle after nerve

repair increased from 40% without stimulation to 75% with

stimulation. Electrical stimulation thus dramatically alters the

distribution of regenerating sensory axons, replacing normally random

behavior with selective reinnervation of tissue-specific targets. If

the enhanced regeneration specificity resulting from electrical

stimulation is found to improve function in a large animal model,

this convenient and safe technique may be a useful adjunct to

clinical nerve repair.