A LIGHT AND ELECTRON MICROSCOPIC STUDY OF AXON REACTION IN THE RED NUCLEUS OF THE RAT FOLLOWING CERVICAL AND THORACIC LESIONS

Abstract

Egan D.A., Flumerfelt B.A. & Gwyn D.G. (1977) Neuropathology and Applied Neurobiology 3, 423–439A light and electron microscopic study of axon reaction in the red nucleus of the rat following cervical and thoracic lesionsAxon reaction in neurons of the caudal 200 pm of the red nucleus was studied by light and electron microscopy from 1–250 days after axotomy at cervical and at thoracic levels. Following cervical lesions, severe chromatolysis occurred on the third day and by 55 days all of the neurons were atrophic. After thoracic lesions, the reaction was less intense and by 55 days the neurons had returned to normal. The initial morphological changes suggested a regenerative response which was characterized by early dissolution of the ER followed by an increase in its elaboration from the nuclear envelope, and the formation of a nuclear cap. Dilated cisternae of ER were observed in both groups and were seen to contain material similar to that in the ER cisternae generally. Neurofilamentous hyperplasia was most prominent at day 7 in both groups. Neurons of those operated at the cervical level became atrophic at the later stages and signs of autophagy were seen. Evidence of neuronal degeneration, characterized by densely packed whorls, vacuoles and dense bodies, was also seen. The fate of the neuron, i.e. regeneration, atrophy or death, appeared to be determined by the percentage of cytoplasm lost.