1 ‐Methyl‐4‐Phenyl‐ 1,2,3,6‐Tetrahydropyridine: Correspondence of Its Binding Sites to Monoamine Oxidase in Rat Brain, and Inhibition of Dopamine Oxidative Deamination In Vivo and In Vitro

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Abstract
A saturable, specific, high-affinity binding site for [3H]1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine was found in rat brain homogenates. The CNS regional distribution, the subcellular fractionation, and the displacement by paragyline, cloryline and deprenyl suggest that this binding site may correspond to monoamine oxidase. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine inhibited the oxidative deamination of dopamine, both in vivo and in vitro. Striatal levels of 3,4-dihydroxyphenylacetic acid were significantly reduced shortly after i.v. administration, and returned to normal values after a few hours. The in vitro formation of 3,4-dihydroxyphenylacetic acid from dopamine was inhibited by concentrations of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine comparable to those of pargyline.