Kinetic Measurements of the Turnover Rates of Phenylethylamine and Tryptamine In Vivo in the Rat Brain

Abstract

Abstract: The turnover rates of phenylethylamine and tryptamine have been estimated as their rates of accumulation after inhibition of monoamine oxidase by pargyline and were found to be 1.53 nmol/g/h and 0.24 nmol/g/h, respectively. Rate constants for the substrate activities of these amines towards monoamine oxidase were calculated as 100 h −1 and 150 h −1 , respectively. Tryptamine was found to exhibit a biphasic response to increasing pargyline dosage, demonstrating its dual activity to type B and type A monoamine oxidase, for which two rate constants were obtained, k B =100 h −1 and k A =50 h −1 .