Carbon monoxide-induced neuropathy in the rat. Ultrastructural changes.

The peroneal and ventral caudal nerves of rats exposed to 2,500 ppm CO until loss of nerve conduction occurred were studied by electron microscopy. Loss of normal axonal and Schwann cell structure was seen at the node of Ranvier. This loss was more prominent in large myelinated fibers, but was also seen in small myelinated fibers at seven and ten days postexposure. At this time, ventral caudal nerve conduction velocity decreased following a transient period of recovery lasting 9 to 13 days. Repair of the node began at 14 to 21 days postexposure, when maximal nerve conduction velocity had returned to normal. Complete normalization of node structure was not seen even 60 days after exposure, in many instances.