Increased platelet 3H-imipramine binding and monoamine oxidase B activity in Alzheimer's disease.

Several biochemical abnormalities in peripheral tissues have been reported in Alzheimer's disease (AD). With this in mind we studied platelet monoamine oxidase B (MAO B) activity and 3H-imipramine (IMI) binding in both AD patients and healthy subjects and found a significantly higher level of platelet MAO B activity and 3H-IMI Bmax values in the AD patients. In view of the part that MAO B plays in metabolizing serotonin (5HT) and of the relationship which exists between 3H-IMI binding and 5HT uptake, our results would suggest that with AD there occurs a complex dysfunction in the 5HT system, at least at a peripheral level.