Expression of the prion protein in the rat forebrain: an immunohistochemical study

The cellular prion protein (PrP super(C)) is crucial for the development of transmissible spongiform encephalopathies (TSEs), where the pathogenic scrapie isoform (PrP super(Sc)) of the same protein, is considered to be the principal or sole infectious agent. Here, we report findings on PrP super(C) expression in the rat forebrain, using immunohistochemical techniques on free floating sections of 60 mu m thickness. Along with neurons and astrocytes in the gray matter, PrP super(C) was detected for the first time in glial cells of the white matter and in cells of circumventricular organs. PrP super(C) positive cellular processes were also found to be closely associated with intraparenchymal blood vessels, often in the form of end feet. Interestingly, PrP super(C) expression was observed in areas where PrP super(Sc) deposition in late stages of infection has been earlier reported in the rat and other species.