Editing Monoamine oxidase (section)

== Subtypes and tissue distribution ==
In humans there are two types of MAO: [[Monoamine oxidase A|MAO-A]] and [[Monoamine oxidase B|MAO-B]].<ref name="pmid15279563">{{Cite journal |author-link=Jean Chen Shih |vauthors=Shih JC, Chen K |date=August 2004 |title=Regulation of MAO-A and MAO-B gene expression |journal=Current Medicinal Chemistry |volume=11 |issue=15 |pages=1995–2005 |doi=10.2174/0929867043364757 |pmid=15279563}}</ref>
* Both are found in [[neuron]]s and [[astroglia]].
* Outside the [[central nervous system]]:
** MAO-A is also found in the [[liver]], [[pulmonary vascular system|pulmonary vascular]] [[endothelium]], [[Human gastrointestinal tract|gastrointestinal tract]], and [[placenta]].
** MAO-B is mostly found in [[blood]] [[platelet]]s.

MAO-A appears at roughly 80% of adulthood levels at birth, increasing very slightly after the first 4 years of life, while MAO-B is almost non-detectable in the infant brain. Regional distribution of the monoamine oxidases is characterized by extremely high levels of both MAOs in the [[hypothalamus]] and hippocampal uncus, as well as a large amount of MAO-B with very little MAO-A in the [[striatum]] and [[globus pallidus]]. The cortex has relatively high levels of only MAO-A, with the exception of areas of the [[cingulate cortex]], which contains a balance of both. Autopsied brains demonstrated the predicted increased concentration of MAO-A in regions dense in serotonergic neurotransmission, however MAO-B only correlated with norepinephrine.<ref name="pmid23403377">{{Cite journal |vauthors=Tong J, Meyer JH, Furukawa Y, Boileau I, Chang LJ, Wilson AA, Houle S, Kish SJ |date=June 2013 |title=Distribution of monoamine oxidase proteins in human brain: implications for brain imaging studies |journal=Journal of Cerebral Blood Flow and Metabolism |volume=33 |issue=6 |pages=863–71 |doi=10.1038/jcbfm.2013.19 |pmc=3677103 |pmid=23403377}}</ref>

Other studies, in which the activities of MAO (not protein amounts) were examined in rat brain, revealed the highest MAO-B activity in the median eminence of hypothalamus. Dorsal raphe nucleus and medial preoptic area have relatively high MAO-B activity, but much lower than MAO-B activity in the median eminence.<ref name=":0">{{cite journal| vauthors = Razygraev AV, Arutjunyan AV |date=2007-09-01|title=Monoamine oxidase activity in several structures of rat brain |journal=Neurochemical Journal |volume=1|issue=3|pages=204–207|doi=10.1134/S1819712407030051 |s2cid=9550341}}</ref><ref name=":1">{{cite journal| vauthors = Razygraev AV, Taborskaya KI, Volovik KY, Bunina AA, Petrosyan MA |date=2016-04-01|title=Monoamine oxidase activity in the rat pineal gland: Comparison with brain areas and alteration during aging |journal=Advances in Gerontology |volume=6 |issue=2 |pages=111–116 |doi= 10.1134/S2079057016020120 |s2cid=88975594}}</ref> Among cerebral endocrine glands, pineal gland has high MAO-B activity (its median value is lower than that for median eminence and higher than that for medial preoptic area).<ref name=":1" /> Pituitary has the lowest level of MAO-B activity when compared with brain areas studied.<ref name=":0" />