Expression of neurofilament proteins in the vestibular ganglion cells of the rat.

Vestibular neurons from adult rats were studied by immunofluorescence microscopy using ten polyclonal and monoclonal antibodies reacting with different subunits of neurofilament (NF) polypeptides. Most antibodies strongly immunolabeled axons and dendrites. With the majority of antibodies the vestibular ganglion cells showed two distinct subpopulations: those with intense immunoreactivity and those without it. The intensely immunoreactive somata, staining with anti-70 kDa and anti-200 kDa NF antibodies but not with anti-150 kDa NF antibodies, comprised 32% of the ganglion cells (range: 27-40%). These cells were larger than the weakly immunoreactive majority of cells. Comparisons of adjacent sections revealed that at least a part of the distinctly immunostained cells were the same regardless of the antibody used. Thus, about one-third of the vestibular ganglion cells seem to form a subpopulation containing 200 kDa and 70 kDa subunits of NF polypeptides. Similar compositions of NF subunits have been demonstrated in such cells as the large dorsal root ganglion cells. The high percentage of neuronal somata with phosphorylated subunits of NF polypeptides demonstrated in this study is exceptional in other normal neurons and has been demonstrated only in experimental models and disease states.