THE EFFECT OF AGING ON EFFERENT NERVE-FIBERS REGENERATION IN MICE

This study evaluates the influence of aging on nerve regeneration and reinnervation of target organs in mice aged 2, 6, 9, 12, 18 and 24 mon ths. In animals of each age group the sciatic nerve was subjected to c rush, section or section and suture. Reinnervation of plantar muscles and sweat glands (SG) was evaluated over three months after operation by functional methods. Reappearance of SG secretion and motor response s occurred slightly earlier in young than older mice. The degree of mo tor and sudomotor reinnervation, with respect to preoperative control values, was also significantly higher in young than old animals. The d ifferences were more pronounced after 12 months of age. The degree of recovery progressively decreased with the severity of the lesion, diff erences being more marked in older mice. Neurorraphy improved recovery , comparatively more in older than in young mice. These results indica te that, after injuries of peripheral nerves, axonal regeneration and reinnervation are maintained throughout life, but tend to be more dela yed and slightly less effective with aging.