Ultrastructural localization of amyloid beta/A4 protein precursor in the normal rat brain.

The ultrastructural localization of amyloid beta/A4 protein precursor (APP) was studied immunohistochemically in normal rat brains using antibodies against different portions of APP. In cerebral cortical neurons and Purkinje cells. APP reaction products were located in the cytoplasm and on cell surface membranes. Some Golgi apparatuses and rough endoplasmic reticulum also showed APP immunoreactivity on their membranes and some vesicles near the trans face of the Golgi apparatuses were stained. In the neuropil of the cerebral cortex and the cerebellar molecular layer, many cell processes, which surrounded synapses and were considered to be astrocytic, were APP-positive. Foot processes around capillaries and subpial astrocytic processes were also immuno-positive. At the ultrastructural level, APP-positive astrocytic processes were identified.