Alpha-synuclein immunoreactivity in neuronal nuclear inclusions and neurites in multiple system atrophy.

We examined neuronal and oligodendroglial nuclear inclusions and neurites in the pontine base of multiple system atrophy brains using an antibody to alpha-synuclein. Immunohistochemistry showed alpha-synuclein positive inclusions in the nuclei of some neurons and oligodendroglia. Immunoelectron microscopy showed that the labeled inclusions were composed of bundles of tightly packed straight filaments with a diameter of 10-20 nm. The filaments were similar, if not identical, in morphology and immunoreactivity, to those found in the soma of neurons and oligodendrocytes with glial cytoplasmic inclusions. In addition, similar immuno-positive filaments were found in dendrites or unmyelinated axons, but not in myelinated axons. The functional significance of these inclusions in terms of transcriptional and axonal dysfunction is unknown.