Distribution of neurofilament antigens after axonal injury

Phosphorylated and nonphosphorylated epitopes of neurofilament (NF) proteins are distributed in different regions of individual neurons. Immunocytochemical methods, with monoclonal antibodies directed against phosphorylated and nonphosphorylated NF, demonstrated nonphosphorylated NF in perikarya and proximal axonal segments of neurons in dorsal root ganglia, while phosphorylated NF proteins were present in axons of these cells. The distribution of these epitopes of NF were examined at various times following injury of axons in the rat sciatic nerve. Between one and 21 days after crush of the proximal nerve, phosphorylated NF were present in neuronal perikarya. We have compared patterns of perikaryal immunoreactivity at one time point (three weeks) following a more distal crush or complete transection of the sciatic nerve. At this time period, following transection/ligation, phosphorylated NF immunoreactivity was not present in perikarya, but abnormal staining was observed after nerve crush. These altered distributions of phosphorylated epitopes of NF are of interest because several recent reports have indicated that similar, but not identical, abnormal staining patterns occur in human neurological diseases, including Alzheimer's disease and Parkinson's disease. In accord with previous studies, this investigation indicates that one response of neurons to injury, or to disease, is an abnormal distribution of phosphorylated epitopes of NF proteins.