Localization of S100 protein in the rat cerebellum: an immunoelectron microscope study.

Immunoelectron microscopy has shown that, in adult rat cerebellum, S100 protein is localized exclusively in the astroyctes of both the cortex and the white matter. The labelling pattern was unaffected by the inclusion of glutaraldehyde in the primary paraformaldehyde fixative. The immunoperoxidase reaction product is observed over both the perikaryal cytoplasm of astrocytes and their processes. S100 proteins was not found in neuronal structures nor in oligodendrocytes.