Muscle force recovery after continuous direct current stimulation of a crushed nerve

The purpose of this work was to examine whether, after sciatic axonotmesis, continuous low-amplitude direct current stimulation across the nerve crush lesion could affect the overall regeneration rate and shorten the time necessary to restore muscle force. Rats were randomly divided into cathode-stimulated (7 animals with a cathode stimulating electrode at the distal end of the nerve crush), anode-stimulated (6 animals with an anode stimulating electrode at the distal end of the nerve crush) and sham-treated (6 animals) groups. The recovery of muscle force was assessed by measuring the isometric tetanic contraction of the plantar flexor muscles once weekly, for five weeks in all groups. There was no statistically significant difference (P > 0.05) among the three groups from the first to the third week after the nerve crush. The cathode-stimulated animals had a statistically significantly enhanced muscle force recovery in the fourth (P = 0.023) and fifth week (P = 0.003) after the nerve crush, when compared to the anode-stimulated and sham-treated groups. From the first to the fifth week after the nerve crush there was no statistically significant difference (P > 0.05) in muscle force between the anode-stimulated and sham groups. After axonotmesis, the average ratio of normalized muscle force to normalized body weight in the cathode-stimulated group reached the pre-crush control value in the fourth week following the nerve injury. This ratio was significantly lower all five weeks compared to the initial one before axonotmesis in anode-stimulated and sham-treated groups. Placing the cathode-stimulating electrode at the distal end of the nerve crush seems to have shortened the overall time of muscle force recovery. A possible mechanism for the enhancement of muscle force recovery in the cathode-stimulated group is proposed.