IMMUNOCYTOCHEMICAL LOCALIZATION OF AMYLOID PRECURSOR PROTEIN IN RAT-BRAIN

The localization of amyloid precursor protein (APP) in rat brain was s tudied with a cytoplasmic domain-specific antibody. Light microscopic immunocytochemistry demonstrated that APP is present in most neurons, in some oligodendrocytes, and in a population of cells with diameters less than 10 mu m that may be glial. Marked differences in immunoreact ivity among neurons were observed, and the strongest immunoreactivity was contained in larger neurons. Neurons with scant cytoplasm, such as granule cells in the olfactory bulb, dentate gyrus, and cerebellum, w ere weakly immunoreactive. Differences in neuropil immunoreactivity we re also observed; this type of staining was strongest in the caudatopu tamen, lateral septum, medial habenula, nucleus reticularis of the dor sal thalamus, and the lateral portion of the ventroposterior nucleus. Neuropil immunostaining was weakest in layer IV of cortex and in areas containing granule cells. The fact that APP seems to be present in th e vast majority of neurons suggests that this protein plays a role com mon to all neurons. The fact that there is a great difference in the s teady-state amount of APP among different types of neurons suggests th at APP may play a specific role in the function of certain classes of neurons. (C) 1994 Wiley-Liss, Inc.