Histochemical observations on cholinesterase activities in the brains of elderly normal and demented (Alzheimer-type) patients.

The extent and distribution of acetylcholinesterase staining in the hippocampus has been compared in normal elderly cases and patients with Alzheimer's disease. In both groups some senile plaques and neurofibrillary tangles stain positively with acetylcholinesterase and in Alzheimer's disease there is a reduction in acetylcholinesterase staining of nerve processes. The positive staining of processes in senile plaques suggests that they are, at least partly, derived from cholinergic, axonal fibres and the decrease in acetylcholinesterase staining of nerve processes may indicate a diminution in cholinergic, afferent input fibres to the hippocampus in Alzheimer's disease.