An enzyme that metabolizes (breaks down) monoamine neurotransmitters such as dopamine, serotonin, epinephrine, norepinephrine, and acetylcholine. Mitochondria, tiny structural units within a cell, produce MAO. Only neurons (nerve cells) contain MAO. There are two main forms of MAO, type A (MAO-A) and type B (MAO-B). MAO-A primarily acts on serotonin, epinephrine, and norepinephrine; MAO-B primarily acts on dopamine and acetylcholine. Through its metabolic actions, MAO affects many autonomic nervous system functions including regulation of heart rate and blood pressure (through its actions to metabolize epinephrine and norepinephrine) as well as functions related to mood, emotion, and behavior (through its actions on serotonin and cerebral dopamine).
The monoamine oxidase (mao) gene regulates mitochondrial monoamine oxidase production. Mutations in the MAO gene appear in some people with Parkinson’s, suggesting that flaws in MAO regulation may contribute to the disease’s symptoms. MAO also plays a key role in depression, which is emerging as a significant symptom of Parkinson’s disease. More than half of people with Parkinson’s experience clinical depression at some point in the disease, and for many it is identified in retrospect as one of the earliest symptoms.
As dopaminergic neuron loss continues in Parkinson’s disease, the brain’s supply of dopamine correspondingly diminishes. The supply of MAO, however, appears to remain normal, as it must for other brain functions to continue. As a result dopamine metabolism continues at a normal rate even though there is less dopamine than the brain requires. monoamine oxidase inhibitor (maoi) medications used to treat depression block the action of MAO nonselec-tively. Their use may have significant adverse consequences, including potentially life-threatening escalation of blood pressure. using medications selectively to regulate the action of MAO-B shows great promise in treatment for Parkinson’s disease, although at present only the drug selegiline (Deprenyl) is used for this purpose; another drug, rasaligine, has already undergone trials in humans and may be approved by the U.S. Food and Drug Administration (FDA) soon. gene therapy to address mutations in the MAO gene and other genes remains on the therapeutic horizon, with much research still necessary to determine its effectiveness. As well, there is much scientists still do not know about the regulation, production, and role of MAO, including whether forms other than type A and type B exist.
