ULTRASTRUCTURAL-LOCALIZATION OF AMYLOID PROTEIN-PRECURSOR IN THE NORMAL AND POSTISCHEMIC GERBIL BRAIN

Intracellular localization of amyloid protein precursor (APP) in the n ormal and postischemic gerbil brain was examined by immunoelectron mic roscopy. In the normal brain, APP immunoreactivity was localized to th e multivesicular body, the nuclear membrane, Golgi apparatus and rough endoplasmic reticulum. After ischemia for 5 min and reperfusion for 2 4 h, some neurons became intensely immunoreactive for APP in the subic ulum and CA3 region of the hippocampus and layers III and V/VI of the cerebral cortex. No intense labeling occurred in glial cells. Intensel y labeled neurons were characterized by eccentric nuclei and accumulat ion of cellular organelles in the center of the neuronal perikarya, as well as a strongly immunoreactive nuclear membrane and cisternal stru ctures, which were presumed to be dispersed Golgi apparatus and/or fra gmented rough ER. APP immunoreactivity in the multivesicular body sugg ests re-internalization of APP and its degradation in the endosomal-ly sosomal pathway. The ultrastructural features of neurons with intense APP immunoreactivity suggested mild neuronal damage, similar to those found in central chromatolysis. This indicates that accumulation of AP P in these neurons is caused by disturbance of axonal transport, altho ugh the information does not allow us to exclude the possibility of an increase in APP production.