Brain and brain monoamine oxidase in aging and in dementia of Alzheimer's type.

Brain MAO-B activity increases with age. The rate of increase varies in different brain regions. Brain MAO-A activity does not change with age in man and is decreased in the rat. Brain MAO-B activity in AD/SDAT is higher than in age-matched controls. The increased MAO-B activity in aging is due to an increased concentration of otherwise unchanged extrasynaptosomal MAO-B. The increase in brain MAO-B activity with age and in AD/SDAT is more pronounced in white matter than in gray matter. Platelet MAO is increased in patients with AD/SDAT.