ELECTROPHYSIOLOGICAL, MORPHOLOGICAL, AND MORPHOMETRIC EFFECTS OF AGING ON NERVE REGENERATION IN RATS

To investigate the influence of age on the process of nerve regenerati on, the right common peroneal nerves of 14 2 month old and 14 10 month old rats were transected and resutured. At four and eight weeks after the nerve repair, the motor nerve conduction velocity (MNCV), latency , and amplitude of the evoked potential from the peroneus longus muscl e were measured. The number of regenerated myelinated fibres, axon dia meter, axon area, axon circumference, and myelin thickness were also m easured. Compared with the control side (left common peroneal nerve an d muscle), MNCV, latency, and amplitude showed higher recovery rates ( recovery rate (%) = operated/control x 100) in 2 month old rats than i n 10 month old rats, particularly at four weeks after the operation. I n the morphometric study, axon diameter, axon area, and myelin thickne ss also recovered more quickly (recovery rate (%) = operated/control x 100) in 2 month old rats, particularly four weeks after the operation . Morphologically, myelin remnants were not found in 2 month old rats eight weeks after the operation, though they remained in 10 month old rats. These studies show that the recovery rate was significantly grea ter in 2 month old rats than in 10 month old rats. The explanation see ms to be the difference in the speed of Wallerian degeneration, axonal regeneration, and myelin regeneration.