title: Preferential deamination of dopamine by an A type monoamine oxidase in rat brain.
abstract: The effect of graded doses of clorgyline, a preferential inhibitor of MAO A, and of deprenil, a preferential inhibitor of MAO B, on the activities of serotonin-deaminating MAO (MAO A) of dopamine-deaminating MAO, and of phenethylamine-deaminating MAO, (MAO  B), in rat corpus striatum were compared with the effects of the drugs on striatal levels of homovanillic acid(HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC). The dose-response curves for the two last-mentioned dopamine metabolites closely follow those for MAO A and dopamine-deaminating activity, whether clorgyline or deprenil was used as MAO inhibitor. In addition, the effect of these drugs on dopamine levels and on the accumulation of 3H-dopamine + 3H-methoxytyramine formed from 3H-DOPA in rat whole brain was analysed. In contrast to the marked increases caused by clorgyline, the effects of deprenil were negligible. In reserpinized rats, clorgyline potentiated the effect of L-DOPA on motor activity; deprenil did not. These results suggest that the deamination of dopamine in vivo is almost entirely effected by MAO A.
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis; D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000378:metabolism; D003010:Clorgyline / Q000494:pharmacology; D003342:Corpus Striatum / Q000032:analysis / Q000201:enzymology; D003641:Deamination; D004295:Dihydroxyphenylalanine / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D005260:Female; D006719:Homovanillic Acid / Q000032:analysis; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009043:Motor Activity / Q000187:drug effects; D009647:Normetanephrine / Q000096:biosynthesis; D010627:Phenethylamines / Q000378:metabolism; D051381:Rats; D012110:Reserpine; D012701:Serotonin / Q000378:metabolism; D014439:Tyramine / Q000378:metabolism
chemical_list: D008996:Monoamine Oxidase Inhibitors; D010627:Phenethylamines; D009647:Normetanephrine; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D007980:Levodopa; D004295:Dihydroxyphenylalanine; D012110:Reserpine; D008995:Monoamine Oxidase; D003010:Clorgyline; D004298:Dopamine; D006719:Homovanillic Acid; D014439:Tyramine