Indoxyl derivatives: Potential psychotropic metabolites

Effects of indole, indican, 1-methylindole, 1-methylindican, indoxylo-acetate, adrenochrome, adrenolutin, adrenochrome methyl ether, and 5,66-dihydroxy-1-methylindole were examined on activity of rats doing a variable-interval, positive-reinforcement task (bar pressing for food reward). All of the 3-hydroxylated indoles with the exception of indican were active. When the 3-hydroxyl group was blocked or removed, as in adrenochrome methyl ether or 5, 6-dihydroxyl1-methylindole, activity was lost completely. 1-Methylindole was also active, but a study of its metabolism showed it to be converted to 1-methylindican, which is probably the active agent. A side observation was that ethanol exhibited a synergistic effect to indoxylo-acetate.