Recovery of muscle after different periods of denervation and treatments

Three aspects of reinnervation and recovery of skeletal muscle following various periods of denervation were investigated: (1) the effect of duration of denervation; (2) the effect of hyperthyroidism on recovery; and (3) whether the muscle or the nerve limits recovery. The rat medial gastrocnemius (MG) nerve was cut and then resutured after 0, 3, 7, 21, or 56 days. In a second group of animals, the MG muscle was denervated and, in addition, the animal received triiodothyronine (T3) supplementation during reinnervation. The third group of animals had the denervated MG muscle reinnervated by a larger number of newly transected foreign axons. The force produced by the reinnervated muscle depends on the period that the muscle was denervated. Recovery was impaired when the period of denervation exceeded 7 days. T3 treatment did not benefit the return of force production, nor did providing the muscle with a larger number of newly transected axons.