MUSCLE REGENERATION IN YOUNG AND OLD RATS - EFFECTS OF MOTOR-NERVE TRANSECTION WITH AND WITHOUT MARCAINE TREATMENT

We tested the hypothesis that after skeletal muscle regeneration in ol d compared with young rats damage to the motor nerve rather than damag e to muscle fibers determines the magnitude of the deficits in muscle mass and maximum force (P-o). The mass and P-o of extensor digitorum l ongus (EDL) muscles of young (4 months) and old (24 months) male rats were compared two months following (i) Marcaine treatment plus simulta neous motor nerve transection, (ii) motor nerve transection alone, and (iii) Marcaine treatment alone (from data compiled previously). In bo th the nerve transection-only and Marcaine with nerve transection grou ps the recovery of mass and P-o was significantly greater in young tha n in old rats. This is in contrast to our previous data showing that i n the absence of nerve damage Marcaine-treated muscle in old rats rege nerates as well as that in young rats. Our hypothesis was supported an d we conclude that impaired axonal regeneration, re-establishment of n erve-muscle contact, or both, is the critical component in the impaire d regeneration of muscle grafts in old as compared with young rats.