Innervation of human hippocampus by noradrenergic systems: normal anatomy and structural abnormalities in aging and in Alzheimer's disease.

Immunocytochemical studies, using an antibody directed against human dopamine beta-hydroxylase, identified an extensive plexus of noradrenergic axons/terminals in normal human hippocampus. In hippocampi of individuals with Alzheimer's disease, the density of noradrenergic innervation was reduced and abnormal noradrenergic axons, which exhibited multifocal enlargements, were present in the neuropil. Some of these neurites were clustered around deposits of amyloid (senile plaques), and these abnormalities were most common in CA3-4, a region normally showing a relatively high density of noradrenergic terminals. This investigation provides direct evidence for structural abnormalities of noradrenergic axons/nerve terminals in hippocampi of individuals with Alzheimer's disease.