The Axon Reaction: A Review of the Principal Features of Perikaryal Responses to Axon Injury

Abstract

This chapter provides an overview of the principal features of perikaryal responses to axon injury. The neuron is an unusual cell. Its axon terminals may be situated at what in cellular terms is an enormous distance from the cell body (perikaryon); the volume of the latter may be but a small fraction of the total cellular volume. Yet the neuronal processes are maintained and their substance is constantly renewed from the perikaryon. The separation of an axon from its cell body results (in vertebrates) in the degeneration of the separated portion and is followed by a series of morphological changes in the perikarya. The most conspicuous of these is the disintegration, redistribution, and apparent disappearance from the cell body of cytoplasmic basophil material. Changes in axotomized neurons are generally assessed by comparison with the corresponding contralateral neurons of the experimental animal.