II. Cortical neurons immunoreactive with antisera against neuropeptide Y are altered in Alzheimer's‐type dementia

Abstract Neurons identified by their immunoreactivity with antisera against neuropeptide Y (NPY) were studied in three selected areas of the cerebral cortex in brains from controls and in senile dementia of the Alzheimer type (ATD). Changes were more profound in temporal cortex than in parietal cortex, and more severe in parietal cortex than in frontal cortex, paralleling the severity of neuritic plaque formation and incidence of neurofibrillary tangles in these regions. NPY‐i neurons became distorted, with enlarged misshapen cell somata and reduced, thickened, and gnarled dendrites. There was a sharp reduction in the extensiveness and delicacy of the axonal plexus; the reorganized axons were haphazard compared to the normal symmetry of these fibers. Besides the alteration in form and sizes, there were also appreciably fewer cells. Nevertheless, the NPY population is not eliminated. Double‐label studies of NPY‐i and thioflavin indicate that NPY‐i fibers can participate in neuritic plaque formation although not all neuritic plaques contained NPY‐i axons and not all NPY‐i axons were associated with plaques. The surviving NPY cells were evident in all cortices examined, thus giving rise to the speculation that these peptide neurons may have unusual survival and reorganization potential even in terminal neurological disease.