RECOVERY OF MUSCLE AFTER DIFFERENT PERIODS OF DENERVATION AND TREATMENTS

Three aspects of reinnervation and recovery of skeletal muscle followi ng various periods of denervation were investigated: (1) the effect of duration of denervation; (2) the effect of hyperthyroidism on recover y; and (3) whether the muscle or the nerve limits recovery. The rat me dial 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 dene rvated and, in addition, the animal received triiodothyronine (T3) sup plementation during reinnervation. The third group of animals had the denervated MG muscle reinnervated by a larger number of newly transect ed foreign axons. The force produced by the reinnervated muscle depend s on the period that the muscle was denervated. Recovery was impaired when the period of denervation exceeded 7 days. T3 treatment did not b enefit the return of force production, nor did providing the muscle wi th a larger number of newly transected axons.