Changes in Monoamine Oxidase with Aging

There have been a continuing and increasing interest in biogenic amine metabolism, particularly in the central nervous system, since these amines may play a role in the etiology of depression, mania, and parkinsonism.

Abstract

There has been a continuing and increasing interest in biogenic amine metabolism, particularly in the central nervous system, since these amines (norepinephrine, serotonin, dopamine) may play a role in the etiology of depression, mania, and parkinsonism. There are several lines of evidence from which the biogenic amine hypotheses of these disorders are drawn. For example, agents which are known to deplete neurons of amines, such as reserprine and alpha-methyl-dopa, can precipitate depressive illness in a significant percentage of patients, particularly if there is a past personal or family history of depression. In addition, pharmacologic agents useful in treating depression, such as the tricyclic antidepressants and monoamine oxidase inhibiting group of drugs are known to affect biogenic amine metabolism and function in the CNS. Finally, there are studies of blood and urinary excretion of amines and their metabolites which suggest that depressed and manic patients may exhibit differences from normals in amine metabolism. Such studies have been periodically reviewed over the past several years (1, 2, 3, 4). In regard to parkinsonism, the earlier reports implicating a defect in biogenic amine metabolism, specifically dopamine (5, 6) culminated in the successful treatment of this condition with the amino acid precursor to dopamine, dihydroxyphenylalanine (DOPA) (7).