Translated from our German original by AI. The German text was researched, written, and edited by the Psychedelia Foundation team and remains the authoritative version.
A study published in June 2026 in ACS Chemical Neuroscience suggests that blocking the serotonin transporter (SERT) can dampen the psychedelic effects of certain tryptamines. The study centered on 4-methoxy-N-methyl-N-isopropyltryptamine (4-MeO-MiPT), a 5-HT2A receptor agonist that also inhibits the serotonin transporter.
The researchers compared 4-MeO-MiPT with its 4-hydroxy analog 4-HO-MiPT (miprocin) and with other structurally related tryptamines. In cell assays, the substances showed pronounced activity at various serotonin receptors, including the 5-HT2A receptor. At the same time, 4-MeO-MiPT, 4-MeO-DiPT, and 4-MeO-McPT inhibited SERT considerably more strongly than their respective 4-hydroxy analogs.
The scientists then tested the substances in C57BL/6J mice. Psychedelic activity was measured by the head-twitch response (HTR), an established behavioral reaction of rodents to 5-HT2A agonists. 4-HO-MiPT and 4-MeO-MiPT were similarly potent at triggering the HTR. The maximum response to 4-MeO-MiPT was considerably lower, however: 34 head twitches within 30 minutes, against 77. 4-MeO-DiPT and 4-MeO-McPT likewise produced a lower maximum HTR than the corresponding 4-hydroxy compounds.
Further evidence that SERT is involved came from pretreating the animals with fluoxetine, a SERT inhibitor. In mice that subsequently received 4-HO-MiPT, 4-HO-DiPT, or 4-HO-McPT, the maximum HTR fell to a level resembling that of the respective 4-MeO analogs.
The results therefore indicate that strong SERT inhibition can limit the psychedelic behavioral response triggered by 5-HT2A activation, at least in the mouse model. The compounds examined are also active at other serotonin receptors, however, particularly 5-HT1A, which can likewise contribute to dampening the HTR. The observed effect cannot be attributed to SERT alone.
The authors see dual 5-HT2A/SERT ligands as a possible field of research for compounds that combine the pharmacological properties of serotonergic psychedelics with weaker acute psychedelic effects. Whether this approach can be used therapeutically will first have to be tested in further preclinical and clinical work. The present study provides preclinical data only, and the head-twitch test in mice says nothing directly about subjective psychedelic effects in humans.
