Influence of age on regeneration in the peripheral nervous system

Studies on the influence of age on regeneration in the peripheral nervous s ystem are reviewed. Observations in the human are limited, but clinical exp erience indicates that the efficiency of regeneration is less in later life . The results of experimental studies in animals, although sometimes variab le, indicate a decline with age. This may be correlated with reduced axonal transport. At motor nerve terminals, the capacity to produce ultraterminal sprouting secondary to partial denervation is reduced, but not the capacit y to eliminate terminal sprouts or reinnervation. Frequency and accuracy of reoccupation of the sites of motor nerve terminals are impaired. Nerve tra nsection is more likely to result in loss of the parent neurons following n erve transection in young than in older animals. Chromatolysis is more inte nse and does not return to normal as rapidly in old animals, and the degree of retrograde axonal atrophy is less. This suggests a diminished dependenc e on peripheral growth factor support. Copyright (C) 1999 S. Karger AG, Bas el.