Qualitative and quantitative comparison of the distribution of phosphorylated and non-phosphorylated neurofilament epitopes within central and peripheral axons of adult hamster (Mesocricetus auratus).

The distribution of phosphorylated and non-phosphorylated neurofilament epitopes was determined immunocytochemically in adjacent 2 microns-thick sections of sciatic nerve, ventral root and spinal cord. Staining was scored as either intense, moderate or absent and the proportion of labeled axons was calculated for each category. Nearly all sciatic nerve and ventral root axons were immunoreactive with both antibodies against phosphorylated and non-phosphorylated neurofilaments and there were no significant differences in the number of intensely- or moderately-labeled axons. Within the spinal cord however, while the majority of large caliber axons was stained with both antibodies, there was a significant number of small caliber axons which stained only with antibodies against phosphorylated neurofilaments. These results show that phosphorylated and non-phosphorylated neurofilaments are extensively codistributed in CNS and PNS axons, and that in the CNS, staining intensity for non-phosphorylated epitopes is less in the smaller axons.