Fig. 4.

Brief 20-Hz electrical stimulation accelerates axon outgrowth across the surgical site of nerve repair. (a) The rat femoral nerve was transected and microsurgically repaired 20 mm from the branching of the nerves into the motor branch to the quadriceps muscle and the cutaneous saphenous nerve branch. The number of backlabeled motoneurons that regenerated their axons into both the branches and were backlabeled 25 mm from the suture site with fluororuby and fluorogold, increased progressively over an 8–10-week period of time. (b) Staggered axon regeneration was due to the “staggering” of regenerating axons across the suture site over a 4-week period as determined by counting motoneurons that were backlabeled by crushing the femoral nerve stump 1.5 mm from the repair site. (c, d) The “staggered axon regeneration” across the suture site was accelerated significantly (*p < 0.05) by a 1-h period of 20-Hz continuous electrical stimulation such that all motoneurons regenerated their axons over a distance of 25 mm within 3 weeks rather than 8-10 weeks with sham stimulation and motoneurons regenerated their axons significantly more qucikly across the suture site into the distal nerve stump