Reference

Inhibition of monoamine oxidase by 3,4-dihydroxyphenyl-L-alanine and its analogs

Inhibition of monoamine oxidase by 3,4-dihydroxyphenyl-L-alanine and its analogs. Naoi, Makoto; Nagatsu, Toshiharu (Sch. Med., Nagoya Univ., Nagoya 466, Japan). Life Sci., 40(4), 321-8 (English) 1987. CODEN: LIFSAK. ISSN: 0024-3205. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacology) L-DOPA [59-92-7] inhibited type A monoamine oxidase [9001-66-5] in human placental mitochondria. The inhibition was noncompetitive with the substrate, kynuramine, and the inhibition was completely reversible. D-DOPA [5796-17-8] inhibited MAO in the same way, and the apparent Ki values of L- and D-DOPA were 154 mM and 133 mM, resp. L-a-Methyl-DOPA [555-30-6] inhibited the MAO activity competitively with the substrate, but studies with other analogs of DOPA revealed that the inhibition required an amino and a carboxyl group at a-position. The substitution of a hydroxy group at 3 or 4 position of catechol ring with a methoxy group abolished the inhibition of the MAO activity. In addn. to type A MAO in human liver and placental mitochondria, type B MAO in liver mitochondria was inhibited by L-DOPA, but type B MAO was less sensitive to L-DOPA. These results are discussed with regard to regulation of the level of biogenic amines in the brain.

Effect of L-DOPA analogs in Sidman avoidance performance in mice

Effect of L-DOPA analogs in Sidman avoidance performance in mice. Thut, Paul D. (Dent. Sch., Univ. Maryland, Baltimore, Md., USA). Life Sci., 21(3), 423-31 (English) 1977. CODEN: LIFSAK. DOCUMENT TYPE: Journal CA Section: 1 (Pharmacodynamics) Mice were trained to avoid foot shock by turning a drum mounted in the wall of a behavioral chamber. L-DOPA (L-I) [59-92-7] (178 to 320 mg/kg i.p.) and D-I [5796-17-8] (320 to 1000 mg/kg, i.p.) but not L-3-O-methyl-DOPA [300-48-1] (178 to 560 mg/kg, i.p.) significantly decreased the no. of responses made by the animals. Pretreatment with Ro 4-4602 (50 mg/kg, i.p.), a peripheral DOPA-decarboxylase inhibitor, enhanced the depressant effect of L-I but not that of D-I. Inhibition of central DOPA-decarboxylase (Ro 4-4602, 500 mg/kg, i.p.) partially reduced the depressant effect of L-I but not that of D-I. Thus, only part of the depressant action of L-I is due to its central decarboxylation.