5-Chloro-αMT
5-Chloro-αMT, also known as 5-chloro-α-methyltryptamine or as PAL-542, is a tryptamine derivative related to α-methyltryptamine and one of only a few known serotonin–dopamine releasing agents. It is also a potent serotonin 5-HT2A receptor agonist and hence may be a serotonergic psychedelic. The drug has been investigated in animals as a potential treatment for cocaine dependence.
Pharmacology
Pharmacodynamics
5-Chloro-αMT is a serotonin–dopamine releasing agent. The values of 5-chloro-αMT in evoking the in vitro release of serotonin, dopamine, and norepinephrine in rat brain synaptosomes were reported as 16nM, 54nM, and 3,434nM, respectively. It had a norepinephrine:dopamine ratio of 64:1 and a dopamine:serotonin ratio of 3.4:1, indicating that it is a highly specific and fairly well-balanced SDRA.However, 5-chloro-αMT has also been found to act as a potent full agonist of the serotonin 5-HT2A receptor, with an EC50 value of 6.27nM and a maximal efficacy of 105%. As a serotonin 5-HT2A receptor agonist, 5-chloro-αMT may produce psychedelic effects. Indeed, its close analogue 5-fluoro-αMT produces a strong head-twitch response in rats, a property which is highly correlated with psychedelic effects in humans, and αMT is well-established as a psychedelic drug in humans.
5-Chloro-αMT was found to not reliably produce intracranial self-administration in rats or substitute for cocaine in rats or monkeys in drug discrimination tests. It was found through study of 5-chloro-αMT in rhesus monkeys that norepinephrine release has minimal influence on the misuse potential of monoamine releasing agents and that loss of norepinephrine release activity does not affect efficacy in reducing cocaine self-administration in SDRAs relative to serotonin–norepinephrine–dopamine releasing agents such as naphthylisopropylamine. However, SDRAs like 5-chloro-αMT would be expected to produce fewer side effects relative to SNDRAs, and thus could be better-tolerated in the treatment of cocaine dependence and other conditions.
5-Chloro-αMT is known to be a potent monoamine oxidase inhibitor, specifically of monoamine oxidase A. Its values for inhibition of MAO-A and monoamine oxidase B are 250nM and 82,000nM, respectively. Its potency in inhibiting MAO-A is similar to that of para-methoxyamphetamine. Other related drugs, such as 5-fluoro-α-methyltryptamine, are known to be potent MAOIs similarly to 5-chloro-αMT. Potent monoamine oxidase inhibition by MRAs has been associated with dangerous and sometimes fatal toxicity in humans.
α-Ethyltryptamine, an SNDRA and close structural analogue of αMT and 5-chloro-αMT, like many other releasers of both serotonin and dopamine such as MDMA, has been found to produce long-lasting serotonergic neurotoxicity in rats.