[Pharmacology of several aromatic amino acid decarboxylase inhibitors]

Abstract

D,L-beta-(3,4-dihydroxyphenyl)lactic acid (I), D,L-beta-(5-hydroxyindolyl-3)lactic acid (II), and L-alpha-methyl-DOPA (III) inhibited the aromatic amino acid decarboxylase (AAAD) competitively. In difference from the compound III, I and II were not AAAD substrates. Compound II selectively suppressed decarboxylation of L-5-hydroxytryptophane. Compounds I and III potentiated the excitation caused in mice by L-DOPA and failed to influence the excitation due to L-5-hudroxytryptophane (L-5-HTP). Compound II attenuated the excitation caused by L-DOPA and L-5-HTP. Pyridoxine hydrochloride and pyridoxalphosphate attenated the excitation caused by L-DOPA and L-5-HTP. Compounds I and III eliminated this action of vitamins B6.