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    Could somebody please explain what happens when there are high and low levels of Monoamine oxidase A? And when will depression result? Is it when there is a high level of MAOA or a low level of MAOA?
    How does the environment play a role?
    Thank you very much, in advance!
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    HI,

    There is substantial evidence over several decades that mood is partly determined by the levels of amines in the brain, including in the pre-frontal cortex. MAO enzymes have the effect of breaking down some of these amines; MAO A oxidizes mainly 5-HT (5-hydroxytryptamine, formerly known as serotonin), while MAO B has a role in the degradation of dopamine.

    Since a high level 5-HT has been shown to elevate mood (and is also implicated in certain other disorders such as autism and dyslexia), MAO A, by breaking it down, reduces the levels of 5-HT, and tends to depress mood. Environmental factors, such as winter, which is implicated in so-called seasonal affective disorder (affect refers to mood), also may lower 5-HT levels, and this could be worsened by MAO A.

    In the clinical context (in the past) MAO inhibitors (MAOIs e.g. phenelzine) were used to treat intractable depression; by inhibiting MAO, these drugs would reduce the breakdown of amines, thus elevating levels of amines, and elevating mood. However, these drugs were risky because certain foods (and some other drugs) like Chianti wine, cheese and avocado tend to raise amine levels, and the resulting very high amine levels could produce overstimulation of the heart, increasing blood pressure unduly, and could result in cerebrovascular accident (CVA - one type of stroke).

    Currently, a newer class of drugs called SSRIs (Selective Serotonin Re-Uptake Inhibitors e.g. fluoxetine, venlafaxine) are used; these prevent the uptake of amines back into pre-synaptic nerve cells, raising their extracellular levels and helping depressed patients.

    In brief, the answer to your Q is that MAO A oxidizes 5-HT, lowering its levels in the brain, and has the potential to cause depression.


    Thank you

    M (ex-medic)
 
 
 
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