Some aspects of monoamine oxidase activity in brain

Ontogenesis of Multiple Forms of Monoamine Oxidase in Rat Brain Regions and Liver

“…a common substrate [ 1 ]. It was observed that the MAO activity in the forebrain, brain stem and cerebellum at day 2 postpartum was about 30.…”

“…The caudal-torostral sequence of development of MAO is not surprising as MAO is responsible for the degradation of monoamine neurotransmit ters, and the monoamine neuronal systems emanate from a series of cell bodies in the brain stem [7], While the brain total and MAO-A activities showed a caudal-to-rostral pattern during development, no such de velopmental profile was observed with MAO-B when this activity was measured with preferred substrate or with tryptamine in the presence of clorgyline. The reason is not immediately clear, but it may be related to the fact that MAO-B preferentially deaminates minor amines [1,12] and that the pres ence of various minor amines in the develop ing brain has yet to be described. As a rela tively large percentage of MAO-B is believed to be associated with extraneuronal materials [3,8,29,31], and because glial cell prolifera tion occurs mainly during late postnatal life [16], it is possible that the absence of the caudal-to-rostral developmental sequence for MAO-B in the brain may be related to the localization of this activity in the extraneuro nal materials.…”

“…In this regard, it is interesting to note that the biosynthesis of monoamines also reached adult levels in the brain stem earlier than in ng/Ho/Wen Ontogenesis of MAO [3,20,24]. As 5-HT and norad renaline are primarily deaminated by MAO-A [1], the concurrent increase in monoamine levels and MAO-A in a particular brain reg ion during postnatal development suggests a causal relationship between these two phe nomena in the rat brain. As MAO-A is be lieved to be mainly intraneuronal |3.…”

“…In the brain, this enzyme is be lieved to regulate the concentrations of monoamine neurotransmitters in monoaminergic neurons [1]. Studies with multiple substrates and selective inhibitors have pro vided much evidence for the existence of two types (A and B) of MAO in rodent brain, liver and other tissues [1,11,12,28].…”

“…In the brain, this enzyme is be lieved to regulate the concentrations of monoamine neurotransmitters in monoaminergic neurons [1]. Studies with multiple substrates and selective inhibitors have pro vided much evidence for the existence of two types (A and B) of MAO in rodent brain, liver and other tissues [1,11,12,28]. Type A preferentially deaminates serotonin, ad renaline and noradrenaline, and is more sen sitive to inhibition by clorgyline [1,2,11,12,17], while type B deaminates benzylamine and /S-phenylethylaminc and is more sensi tive to inhibition by dcprenyl [1,11,12,17,20,32], At present, two hypotheses concern ing the molecular nature of the two types of MAO activities have been proposed [1,11,12,28].…”