Changes in monoamine oxidase and monoamines with human development and aging.

A series of studies of monoamines and their metabolism in a variety of human tissues indicate that there are aging effects that may alter neurotransmitter substances. Monoamine oxidase (MAO) activity has a significant positive correlation with age in plasma and blood platelets of normal subjects and patients suffering from depressive disorders. Monoamine oxidase and age correlate positively in hindbrain and in eight separate ares of human brains from patients who died from a variety of causes. Hindbrain norepinephrine concentration progressively decreases with advancing age (r equals -0.44, P less than 0.01) while no changes were noted for serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). Hindbrain norepinephrine concentration has a significant negative correlation with MAO (r equals -0.41, P less than 0.025) and hindbrain 5-HIAA has a significant positive correlation with MAO (r equals +0.66, P equals less than 0.05). These studies suggest that aging processes may significantly affect monoamine mechanisms and be a predisposing factor to the development of clinical diseases in man such as depression, parkinsonism and other disorders of central nervous system homeostasis.