THE EFFECT OF AGE ON PERIPHERAL NERVE REGENERATION AFTER PERIPHERAL NERVE CRUSH IN ALBINO RATS

Abstract

The nerve fiber is the functional component of the peripheral nerve responsible for transmitting stimuli. The nerve fiber is composed of an axon, Schwann cell, and myelin sheath in myelinated nerve fibers (Schwartz, 1999).

When peripheral nerves are subjected to a crush injury, axons and their myelin sheaths degenerate distally in the presence of macrophages, a process called Wallerian degeneration. Proximal to the crush, axons begin regeneration, cross the injury zone and associate with columns of Schwann cells in the distal stump. These Schwann cells ensheath bundles of regenerating axons and then develop a one to one relationship with those destined to become myelinated. New myelin sheaths appear and become thicker and longer as axonal regeneration progress (Kaoru et al., 1992).

Axotomy of peripheral nerve fibers triggers a variety of responses in the neuronal perikarya and in the axons proximal to the site of ir.jury, with secondary effect on myelination. In the perikarya a sequence of changes occurs, collectively referred to as central chromatolysis or axon. These include peripheral migration of the nuclei and dispersion of the ribosomes associated with the rough endoplasmic reticulum of Nissl bodies. The chromatolytic reaction varies with the age of the animal, proximity of the lesion to the cell body and neuronal type. (Andres, 1961; Watson, 1968; Liberman, 1971; Price and Porter, 1972; Torvik, 1976).