Abstract

The metabolism of serotonin and tryptamine has been studied in animals which have been treated with monoamine oxidase (MAO) inhibitors. In whole mice the rate of serotonin disappearance is not affected by inhibiting MAO, although the formation of 5HIAA is markedly inhibited. It has been shown in these animals that serotonin-O-glucuronide is the major metabolite formed from serotonin when MAO is inhibited. Tryptamine, however, is metabolized at a much slower rate in animals which have been treated with MAO inhibitors, and IAA is the major in vivo metabolite of tryptamine whether or not MAO is inhibited.

Tissues from animals which have been treated w-ith MAO inhibitors still possess weak amine oxidation ability. This system which appears to be insensitive to MAO inhibitors may account for the formation of 5HIAA and IAA observed when serotonin and tryptamine are administered to animals treated with MAO inhibitors.