Acetylcholine and Alzheimer's disease.

The hypothesis that cognitive impairment in Alzheimer's disease is related to cholinergic degeneration in the brain is still, a decade after its formulation, subject to critical evaluation. In marked contrast to the monoamine hypotheses of affective disorders or schizophrenia--based primarily on the mechanisms of action of therapeutic drugs, and yet lacking convincing pathological data on the human brain itself--the cholinergic hypothesis of Alzheimer's disease currently rests largely on evidence of neurochemical pathology in affected tissue, but still depends on effective therapy for its ultimate validation. The urgent need for a means of countering cognitive impairment in degenerative dementias such as Alzheimer's disease (probably the most important cause of intellectual decline in old age) hardly needs emphasising. In this annotation, a number of key questions specifically relating to the cholinergic involvement in Alzheimer's disease are considered. These questions are already being answered both within and, as so often in the history of biological psychiatry, outside the immediate area of investigation.