Abnormal ultrastructural appearances in axons of feline pericruciate cortex after lateral funiculotomy

Abstract

Following left lateral funiculotomy, axons of cat pericruciate cortex exhibited neurofilamentous hyperplasia and complex, adaxonal, oligodendrocytic invaginations into electron-lucent or (commonly) electron-dense, degenerating axoplasm. These changes were absent form sham-operated and unoperated animals. Neurofilamentous hyperplasia was exclusively right-sided and appeared in myelinated axons 5--49 days postoperatively and in nonmyelinated axons 14--153 days after surgery. Oligoglial invaginations were present 1--49 days after surgery and were predominantly right-sided. Intramyelinic, axo-dendritic synapses appeared in operated cats 5--10 days postoperatively. Intra-axonal accumulations of ribosomes were found also. These changes also occurred exclusively or predominantly contralateral to spinal surgery. Other ultrastructural abnormalities, e.g., amorphous transformation of axoplasm and accumulations of dense bodies in intra-myelinic, dark cytoplasm, had a less certain relationship to lateral funiculotomy. The axonal alterations that were limited to operated cats possibly represent a true retrograde axonal degeneration occurring at a distance from the site of axonic interruption and unaccompanied by evidence of nerve cell death.