The axon reaction in motor and sensory neurones of mice studied by a monoclonal antibody marker of neurofilament protein

Following unilateral sciatic nerve crush in mice, changes in the neurofilament content of neuronal perikarya were studied, using a monoclonal antibody to neurofilament protein (RT97). In the spinal cord, anterior horn motor neurones, normally unstained, showed a positive staining reaction with immunoperoxidase on the operated side. This reaction was short lived and maximal on the 11th post-operative day. In spinal ganglia, the proportion of positively staining sensory neurones showed an earlier but otherwise similar increase. In both cases, the response was well defined and contrasted with the changes on Nissl staining, which were markedly different in the two populations of neurones. In the nerve crush region, although regenerating axons were visible with silver staining only 5 days post-operatively, neurofilament protein was not demonstrated in these axons until several days later, after the peak perikaryal increase. These results suggest that an increase in perikaryal neurofilament protein is a consistent and quantifiable event following distal axon trauma, possibly indicating either synthesis of protein subunits or repolymerization of neurofilaments prior to their transport distally down the regenerating axons. The findings may be useful in identifying neurones with distal axon lesions in experimental and other neuropathological material.