The Influence of Age on the Course of Reinnervation of Muscle

Abstract

A study was made on regenerative processes (regeneration in the nerve and reinnervation of the muscle) in young (one-month-old) and old (two-year-old) animals. Recovery of motor function takes place 14th day in young and 32nd in old animals after crushing the nerve. All regenerative processes are slower in old animals. Latent period (the time before reinnervation of peripheral stump) is very much delayed in old animals. Reinnervation of the peripheral stump takes place one day after crushing in young animals whereas few fibres are found in the peripheral stump of old animals 8 days after crushing. The recovery of proteins in the denervated muscle following reinnervation is delayed and slower in the old animal. Percentual increase in mg of N formed by the original muscular substance is 39% in young animals between 14th-32nd day after crushing. No increase in proteins occurs during this time in old animals. An increase in proteins occurs only from 32nd day. The increase from the 32nd-48th day represents only 17%[long dash]expressed as mg of N formed by the original muscular substance. Increase of the amount of DNA in muscle occurs following denervation in young and old animals, the increase being more pronounced in the young animals. Normalization of DNA content in the reinnervated muscle following reinnervation occurs in young as in old animals. The results suggest that a decrease of the trophic function of the nervous system in old animals is an important factor in the metabolic changes occurring in old age.