Ultrastructural localization of butyrylcholinesterase in senile plaques in the brains of aged and Alzheimer disease patients.

Histochemical localization of butyrylcholinesterase has been carried out in primitive, perivascular, and classic plaques in the brains of both nondemented and Alzheimer disease (AD) patients. Butyrylcholinesterase histochemistry has been compared to amyloid beta-protein (A beta P) immunocytochemistry in adjacent sections. In small primitive plaques, most of the butyrylcholinesterase reaction product appears ultrastructurally located over plasma membranes of healthy-looking cell processes. In more extensive primitive plaques, butyrylcholinesterase reaction product also decorates amyloid filaments, which become identifiable as delicate wisps. In classic plaques, large aggregates of butyrylcholinesterase reaction product colocalize with bundles of amyloid filaments, as well as with the compact amyloid core. Thus, deposition of butyrylcholinesterase in senile plaques follows a close parellelism with the progressive aggregation of amyloid beta-protein, supporting the possibility that cholinesterases may play some role in the maturation of these structures.