The axonal response after ventral root avulsions at the cervical 7 level in the cat spinal cord

The ventral cervical 7th root was avulsed from the adult cat spinal cord and the reaction of the torn axons in the underlying white matter was studied by light microscopy using histochemical staining for acetylcholinesterase and immunocytochemical staining for neurofilament and by electron microscopy, after different survival times. One day postoperatively some of the torn axonal ends were enlarged in the intraspinal trajectory of the root fibers in the white matter between the ventral horn and the pial surface as observed by acetylcholinesterase staining. The formation of terminal clubs had accordingly started at this postlesional survival time. From day 2, terminal clubs positive to neurofilament antibody were found. The number of terminal clubs increased during the first 4 days after the avulsion, remained present at 30 days and then disappeared gradually during the next months. One such unmyelinated axonal terminal club was studied at the ultrastructural level. From its distal end an unmyelinated protrusion emanated which appeared myelinated on the most distal part. This protrusion may be the ultrastructural parallel of the ramifications from terminal axonal clubs described by Ramon Y Cajal after avulsion.