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5‐(2‐Aminopropyl)indole (5‐IT): a psychoactive substance used for recreational purposes is an inhibitor of human monoamine oxidase (MAO)

Tomás Herraiz, Simon D. Brandt

Drug Testing and Analysis September 20, 2013 DOI: 10.1002/dta.1530 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics In vitro study Peer reviewed
Population Human MAO-A and -B isozymes
Intervention 5-(2-Aminopropyl)indole (5-IT)
Topics MDMA Serotonin
Keywords Moclobemide Clorgyline Monoaminergic Pharmacology Monoamine oxidase a Tryptamine Harmaline Selegiline Monoamine oxidase b Monoamine neurotransmitter Biochemistry Enzyme Antidepressant
Citations 25
Key points 5-IT is a selective, competitive, and reversible inhibitor of MAO-A (IC50 = 1.6 μM, Ki = 0.25 μM) with no observed MAO-B inhibition.

Abstract

5-(2-Aminopropyl)indole (5-IT) is a psychoactive compound that has recently been associated with several fatal and non-fatal intoxications in a number of European countries. There are indications that acute effects may include symptoms of monoaminergic (e.g. serotonin) toxicity and one mechanism involved in the increase of serotonin levels includes the inhibition of monoamine oxidase. This study investigated the effect of 5-IT on human MAO-A and -B isozymes using kynuramine as the substrate. Substrate conversion to 4-hydroxyquinoline was monitored by high-performance liquid chromatography coupled to diode array detection. This method was employed to determine the extent of MAO inhibition (IC50 and Ki ) and it was found that 5-IT was a selective, competitive and reversible inhibitor of MAO-A. 5-IT revealed a relatively potent ability to inhibit MAO-A (IC50 =1.6 μM and Ki =0.25 μM) while MAO-B inhibition was not observed (0-500 μM 5-IT). Under identical experimental conditions, other established inhibitors of MAO-A and antidepressants provided the following IC50 values: clorgyline 16 nM, harmaline 20 nM, toloxatone 6.7 μM and moclobemide >500 μM. These data indicated that 5-IT was less potent than clorgyline and harmaline but more potent than toloxatone and moclobemide under the in-vitro conditions studied. The inhibition of MAO-A suggests that 5-IT by itself or in combination with other substances may be able to potentiate serotonergic/monoaminergic effects and further studies are needed to clarify its relevance to the adverse effects reported for 5-IT.

Comparable studies

Other preclinical and animal studies on MDMA, most cited first.

Study Year Design Participants
Neurotoxicity of the psychedelic amphetamine, methylenedioxymethamphetamine. Rats (implied by typical neurochemical study context) 1987 Experimental study
3,4-Methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine destroy serotonin terminals in rat brain: quantification of neurodegeneration by measurement of [3H]paroxetine-labeled serotonin uptake sites. Rat brain 1987 Animal experiment
Comparison of the monoamine transporters from human and mouse in their sensitivities to psychostimulant drugs Human and mouse dopamine, norepinephrine, and serotonin transporters expressed in cells 2006 In vitro laboratory study
Small Changes in Ambient Temperature Cause Large Changes in 3,4-Methylenedioxymethamphetamine (MDMA)-Induced Serotonin Neurotoxicity and Core Body Temperature in the Rat Rats 1998 Experimental study
Altered Serotonin Innervation Patterns in the Forebrain of Monkeys Treated with (±)3,4-Methylenedioxymethamphetamine Seven Years Previously: Factors Influencing Abnormal Recovery Squirrel monkeys treated with MDMA 1999 Observational cohort

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