Monoamine oxidase in platelets and brains of non-psychiatric and non-neurological geriatric patients.

Monoamine oxidase (MAO) activity has previously been found to be high both in brain and in platelets in patients with Alzheimer's disease and low in patients with cycloid psychosis and suicidal behaviour and/or ethanol abuse. To establish if there is a correlation between brain and platelet MAO activities in patients without psychic disease, blood samples from patients in a geriatric ward were collected before death and from 4 different parts of the brain at autopsy. The MAO activities in platelets and brain were then estimated with different substrates. No correlation between the MAO activities in the two tissues was, however, found, regardless of the substrate used.