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The Metabolism of Dopamine by Both Forms of Monoamine Oxidase in the Rat Brain and Its Inhibition by Cimoxatone
Author(s) -
Fowler Christopher J.,
Benedetti Margherita Strolin
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb08123.x
Subject(s) - monoamine oxidase , dopamine , monoamine neurotransmitter , chemistry , metabolism , neuroscience , biochemistry , medicine , biology , serotonin , enzyme , receptor
In the rat brain, dopamine is metabolised by both A and B forms of monoamine oxidase (MAO), although the A form of the enzyme is the major component. The K m of MAO‐A toward dopamine (120 μM) is lower than the K m , of MAO‐B toward this substrate (340 μM). The activity of MAO‐A was lower in old rats than in young rats, and the same degree of decrease was found for 5‐hydroxy‐tryptamine as for dopamine as substrates for this enzyme form. The activity of MAO‐B was higher in the old rats, the degree of increase being the same for dopamine as for β‐phenethylamine as substrates for this enzyme form. The K 1 values of the inhibition of MAO‐A by cimoxatone and MD770222 (the principal plasma metabolite of cimoxatone) were independent of the substrate used to assay for activity, but were lower than the K 1 values for the inhibition of MAO‐B by these compounds.