In‐Vivo Decarboxylation of α‐Methyl DOPA and α‐Methyl Metatyrosine

Abstract

α‐Methyl DOPA (DOPA = 3,4‐dihydroxyphenylalanine) and α‐methyl metatyrosine were injected to mice (400 mg/kg intraperitoneally). The former amino acid was also injected to rabbits (200 mg/kg intravenously). At varying intervals after the injection the brains were examined for monoamines (5‐hydroxytryptamine, noradrenaline, dopamine, and α‐methyl analogues). A transient decrease in 5‐hydroxytryptamine and dopamine and a prolonged and more marked decrease in noradrenaline were observed. The α‐methyl amino acids were found to undergo decarboxylation and subsequent β‐hydroxylation in vivo. The drop in noradrenaline and dopamine levels in brain caused by the α‐methyl amino acids appears to be largely due to displacement by these decarboxylation products, which may possibly also take over the functions of the physiological amines.