Neurotransmitter deficits in Alzheimer's disease: criteria for significance

A series of histopathologic, morphologic, and pharmacologic criteria are proposed to establish the significance of neurochemical deficits in Alzheimer's disease. The underlying pathogenic biochemistry of a better understood neurotransmitter-deficiency syndrome, Parkinson's disease, validates these criteria. The major neurotransmitter systems are evaluated against these guidelines. Only the cholinergic system fulfills all the criteria. Noradrenergic mechanisms are also implicated. Subsequent neurochemical abnormalities found in the brains of patients with Alzheimer's disease can be evaluated against these criteria.