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

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.