5-Methoxytryptamine is metabolized by monoamine oxidase A in the pineal gland and plasma of golden hamsters.

Pineal concentrations of 5-methoxytryptamine, 5-methoxytryptophol, 5-methoxyindole acetic acid and melatonin were determined using high performance liquid chromatography following administration of different monoamine oxidase (MAO) inhibitors (clorgyline, pargyline and deprenyl) to golden hamsters. Plasma concentrations of 5-methoxytryptamine, 5-methoxytryptophol and melatonin were also measured following 5-methoxytryptamine administration to hamsters pretreated with MAO inhibitors. A significant increase in pineal and plasma 5-methoxytryptamine together with a decrease in 5-methoxytryptophol concentrations was observed after clorgyline or pargyline. In contrast, following deprenyl administration, no change in pineal and plasma 5-methoxyindoles was observed. These results indicate that monoamine oxidase A is responsible for oxidative deamination of 5-methoxytryptamine.