Abstract
A general review of cholinergic receptors in human brain is presented. The paper focuses upon changes in normal aging brain and in Alzheimer disease. Studies from five different approaches are reported: (1) molecular biology; (2) receptor binding studies; (3) studies with specific neurotoxins; (4) immunocyto‐chemistry; and (5) PET scan. These studies document profound and characteristic differences between the normal aging and the pathological Alzheimer brain with regard to cholinergic receptor localization, distribution, and function.