Science
March 21, 2013
Daniel Wacker, Chong Wang, Vsevolod Katritch et al.
689 citations
Serotonin receptors are targets for drugs treating depression, obesity, and migraine headaches. Crystal structures of two serotonin receptor subtypes bound to antimigraine medications or a precursor of LSD reveal how subtle differences in ligand binding cause substantial differences in receptor signaling and biological responses. The structures show that the same ligand can activate one or both of the two main serotonin receptor signaling mechanisms, depending on which receptor it binds.
Science
March 22, 2013
Chong Wang, Yi Jiang, Jinming Ma et al.
522 citations
Two research teams independently determined the crystal structures of two serotonin receptors bound to antimigraine drugs or a precursor of LSD. The structures show that subtle differences in how ligands bind to these receptors lead to substantial differences in the signals generated and the resulting biological responses. The same ligand can activate one or both of the two main serotonin receptor signaling mechanisms, depending on which specific receptor it binds to.
Science
February 16, 2023
Maxemiliano V. Vargas, Lee E. Dunlap, Chunyang Dong et al.
467 citations
Decreased dendritic spine density in the cortex is a hallmark of several neuropsychiatric diseases, and the ability to promote cortical neuron growth has been hypothesized to underlie the rapid and sustained therapeutic effects of psychedelics. Activation of 5-HT2ARs is essential for psychedelic-induced cortical plasticity, but it is unclear why some 5-HT2AR agonists promote neuroplasticity while others do not. Using molecular and genetic tools, the authors demonstrate that intracellular 5-HT2ARs mediate the plasticity-promoting properties of psychedelics, explaining why serotonin does not engage similar plasticity mechanisms. This work emphasizes location bias in 5-HT2AR signaling, identifies intracellular 5-HT2ARs as a therapeutic target, and raises the possibility that serotonin might not be the endogenous ligand for intracellular 5-HT2ARs in the cortex.
Nat Commun
December 15, 2023
Jason Wallach, Andrew B. Cao, Maggie M. Calkins et al.
153 citations
Serotonergic psychedelics show therapeutic potential, but the specific roles of 5-HT2A receptor signaling pathways are unclear. Researchers developed selective ligands with varying Gq efficacies, including β-arrestin-biased ones. In male mice, 5-HT2A-Gq recruitment efficacy, not β-arrestin2 recruitment, predicted psychedelic potential measured by head-twitch response magnitude. Disrupting Gq-PLC signaling reduced this response, and a threshold Gq activation level was needed for psychedelic-like effects, explaining why partial agonists like lisuride are non-psychedelic. β-arrestin-biased agonists blocked psychedelic effects and caused receptor downregulation and tachyphylaxis. Fine-tuning 5-HT2A Gq-signaling enables development of non-psychedelic 5-HT2A agonists.
ACS Pharmacology & Translational Science
December 14, 2020
Adam K. Klein, Muhammad Chatha, Lauren J. Laskowski et al.
103 citations
The 5-HT2A receptor is the primary target for psilocybin and other serotonergic hallucinogens. Seventeen tryptamines with 4-hydroxy or 4-acetoxy groups and various N,N-dialkyl substituents were tested. All acted as full or partial agonists at 5-HT2 subtypes, with similar potencies at 5-HT2A and 5-HT2B receptors, though bulkier N-alkyl groups reduced potency at 5-HT2C receptors and increased 5-HT2B efficacy. O-acetylation reduced in vitro 5-HT2A potency by 10- to 20-fold without altering efficacy. All compounds induced head twitches in mice, consistent with LSD-like effects. Acetylation had little effect on head-twitch potency, suggesting O-acetylated tryptamines may act as prodrugs deacetylated in vivo. These derivatives have psilocybin-like properties, supporting their classification as psychedelic drugs.
Journal of Natural Products
February 20, 2020
Alexander M. Sherwood, Adam L. Halberstadt, Adam K. Klein et al.
79 citations
A new synthetic method allows access to tryptamine natural products found in psilocybin-producing mushrooms. Laboratory and animal experiments tested whether these compounds are psychoactive. In mice, the natural product baeocystin did not produce a head twitch response, a behavioral marker of psychedelic activity, even though its predicted breakdown product, norpsilocin, strongly activates the 5-HT2A receptor, which is associated with psychedelic effects. This suggests that baeocystin itself may not be psychedelic, despite its metabolite's activity.
ACS Chemical Neuroscience
December 15, 2022
Michael J. Cunningham, Hailey A. Bock, Inis C. Serrano et al.
65 citations
Ariadne, a non-hallucinogenic analog of the hallucinogen DOM, demonstrates significant therapeutic potential in treating various conditions. In clinical trials, Ariadne led to rapid remission of psychotic symptoms in schizophrenia and improved cognition in elderly patients. It acts as a 5-HT<sub>2A</sub> receptor agonist with modest selectivity for 5-HT<sub>1</sub>, exhibiting lower signaling potency than DOM. Notably, in a Parkinson’s disease model, Ariadne alleviated severe motor deficits comparable to l-DOPA, positioning it as a promising candidate for future psychiatric and neurological therapies.
Drug Testing and Analysis
June 5, 2017
Simon D. Brandt, Pierce V. Kavanagh, Brendan Twamley et al.
56 citations
Lysergic acid morpholide (LSM-775), a structural relative of LSD, appeared on the market for new psychoactive substances in 2013, but its potency and psychoactive effects in humans have been disputed. This investigation characterized a powdered sample using multiple analytical techniques and tested its receptor activity. LSM-775 acted as a nonselective agonist at 5-HT1A and 5-HT2A receptors. In head twitch studies with C57BL/6J mice, LSM-775 did not induce the head twitch response unless 5-HT1A receptors were blocked by the antagonist WAY-100,635 (1 mg/kg, subcutaneous). The findings suggest that activation of 5-HT1A receptors by LSM-775 masks its hallucinogen-like effects, consistent with reports that it produces only weak LSD-like effects in humans.
Neuropharmacology
November 19, 2019
Adam L. Halberstadt, Muhammad Chatha, Adam K. Klein et al.
37 citations
The ergoline d-lysergic acid diethylamide (LSD) is one of the most potent psychedelic drugs. 1-Acetyl-LSD (ALD-52) and other 1-acyl-substituted LSD derivatives, including 1-propanoyl-LSD (1P-LSD) and 1-butanoyl-LSD (1B-LSD), have appeared as designer drugs assumed to act as prodrugs for LSD. Competitive binding studies and calcium mobilization assays showed 1-acyl-substitution reduced affinity for most monoamine receptors, including 5-HT2A sites, by one to two orders of magnitude, and these derivatives had weak efficacy or acted as antagonists in Ca2+-mobilization assays. Despite this, they induced head twitches in mice with relatively high potency. High levels of LSD were detected in rat plasma after subcutaneous administration of ALD-52 and 1P-LSD, demonstrating rapid and efficient deacylation in vivo, consistent with the prediction that these compounds serve as prodrugs for LSD.
Beilstein Journal of Organic Chemistry
October 8, 2012
Adam Pigott, Stewart Frescas, John D. Mccorvy et al.
19 citations
Replacing the ethylamine side chain of two psychedelic amphetamine derivatives, DOI and DOB, with a cyclopropylamine moiety produced compounds with high affinity for the 5-HT(2) family of serotonin receptors. The more potent stereoisomer of these cyclopropane analogues had the expected (-)-(1R,2S)-configuration. However, the cyclopropane congeners also showed increased affinity at several other serotonin receptor subtypes beyond 5-HT(2A) and 5-HT(2B). While at appropriate doses the compounds may serve as tools to probe 5-HT(2) receptor function, their selectivity for 5-HT(2A) receptors is somewhat less than that of DOI itself.
bioRxiv (Cold Spring Harbor Laboratory)
July 31, 2023
Jason Wallach, Andrew B. Cao, Maggie M. Calkins et al.
11 citations
preprint
Serotonergic psychedelics show therapeutic promise, but the specific signaling pathways responsible for their effects have been unclear. Researchers developed a series of 5-HT2A receptor ligands with varying Gq efficacies, including β-arrestin-biased ligands. They found that 5-HT2A-Gq efficacy, not β-arrestin2 efficacy, predicts psychedelic potential, measured by head-twitch response in male mice. Disrupting Gq-PLC signaling reduced this response, and a threshold of Gq activation is needed for psychedelic-like effects, explaining why some partial agonists like lisuride are non-psychedelic. β-arrestin-biased agonists caused receptor downregulation and tachyphylaxis, and showed an anti-psychotic-like profile. This fine-tuning of 5-HT2A signaling can generate ligands distinct from classical psychedelics.
Trends Pharmacol Sci
August 28, 2025
Alex C. Kwan, John R. Mantsch, John D. Mccorvy
7 citations
This paper outlines a preclinical framework for discovering new psychedelic drugs, emphasizing the need for systematic research into their chemical structures, biological mechanisms, and therapeutic potential. It argues that understanding the basic science of psychedelics is essential before advancing to clinical applications, providing a roadmap for drug development that prioritizes safety and efficacy.
Annu Rev Pharmacol Toxicol
August 12, 2025
Daniel Wacker, John D. Mccorvy
4 citations
Psychedelics are promising for treating psychiatric disorders, pain, and migraine, but which signaling mechanisms produce their rapid and lasting therapeutic effects remains uncertain. Activation of the serotonin 5-HT2A receptor is key for their psychoactive effects, yet the specific signaling pathways and receptor shapes involved are still being studied. This review summarizes progress on 5-HT2A signaling, the development of biased agonist tools to separate therapeutic from adverse effects, and structural insights for designing tailored psychedelic-derived compounds. It also discusses other 5-HT receptors that may shape therapeutic outcomes and draws lessons from opioid research, emphasizing the need for rigor and reproducibility to advance novel psychedelic pharmacotherapies.
ACS Chem Neurosci
September 13, 2025
Emma M. Bonniwell, Rana Alabdali, Joseph J. Hennessey et al.
3 citations
The serotonin 2C receptor (5-HT 2C ) is involved in processes like mood and appetite and is a target for drugs treating obesity, addiction, and depression, including psychedelics. This analysis of 5-HT 2C signaling confirms that the receptor activates multiple G protein pathways—Gi/o/z and G12/13 in addition to its main Gq/11 pathway—and preferentially recruits β-arrestin2 over β-arrestin1. Increased RNA editing of the receptor reduces signaling across all G protein pathways, especially G12/13, while preserving β-arrestin recruitment. Profiling of ligands shows that psychedelics like LSD and psilocin produce a strong Gq/11 bias by minimally activating other G proteins. These findings provide a foundation for considering broader signaling modalities in 5-HT 2C drug development.
ACS Pharmacology & Translational Science
August 22, 2025
Devin P. Effinger, Serena S. Schalk, Jillian L. King et al.
3 citations
Microdosing involves taking psychedelics at doses too low to cause hallucinations, and is popular for supposed cognitive and emotional benefits. Psychedelics bind strongly to 5-HT 2B receptors, which can cause heart disease when chronically activated. In mice, researchers gave either serotonin or d-fenfluramine as positive controls, or low doses of LSD. Serotonin caused significant ventricular thickening at 4 and 8 weeks; d-fenfluramine caused aortic valve regurgitation at 4 weeks. No significant heart changes appeared in any LSD group. LSD, psilocybin, and norfenfluramine had similar affinity and potency at mouse and human 5-HT 2B receptors. Low-dose LSD produced substantial but short-lived receptor activation compared to d-fenfluramine. These data provide no evidence that prolonged low-dose LSD causes heart remodeling in mice.
bioRxiv (Cold Spring Harbor Laboratory)
April 14, 2025
Devin P. Effinger, Serena S. Schalk, Jillian L. King et al.
2 citations
preprint
Chronic administration of low-dose LSD in mice does not produce the cardiovascular damage seen with serotonin, a known cardiotoxin. Serotonin caused significant ventricular thickening after 4 and 8 weeks, while LSD at two sub-hallucinogenic doses showed no such changes. Although LSD activates 5-HT 2B receptors—the same receptors linked to heart disease from chronic activation—the activation is substantial but short-lived compared to the cardiotoxin d-fenfluramine. Affinity and potency of LSD, psilocybin, and norfenfluramine at mouse and human 5-HT 2B receptors were similar. These findings indicate no evidence of cardiovascular risk from prolonged low-dose LSD in mice.
Journal of the American Chemical Society
December 16, 2025
J.O.S. Beckett, Ryan Buzdygon, Steven Nguyen et al.
1 citation
A new chemical method uses light to trigger a cyclization reaction that attaches a functional group to the fourth carbon of the indole ring, enabling the efficient synthesis of ring-constrained tryptamine analogs. Amino acids were linked to tryptamine and exposed to UV light to produce lactams bridging specific positions on the indole structure. The resulting reduced lactams, called azocinoindoles, were tested for activity at the serotonin 5-HT2A receptor. In computer models and lab experiments, these compounds acted as full or partial activators of the receptor's Gq signaling pathway. In mice, they suppressed the head-twitch response, a behavior linked to hallucinogenic effects, suggesting these compounds are nonhallucinogenic 5-HT2A agonists.
ACS Chemical Neuroscience
May 27, 2026
Grant C. Glatfelter, Serena S. Schalk, Donna Walther et al.
Tryptamine psychedelics produce their effects mainly by activating serotonin 2A receptors, but many also affect other targets. 4-MeO-MiPT, a compound that both activates 5-HT2A receptors and blocks the serotonin transporter (SERT), produces blunted psychedelic effects in humans. In mice, 4-MeO-MiPT and its analogs with stronger SERT blockade showed fewer head twitch responses (a proxy for psychedelic-like effects) than their 4-hydroxy counterparts. Pretreating mice with the SERT inhibitor fluoxetine reduced head twitch responses from 4-hydroxy compounds to levels seen with the 4-methoxy analogs. The findings suggest that dual 5-HT2A/SERT ligands may have therapeutic potential with reduced acute psychedelic effects.
ACS Chem Neurosci
March 4, 2026
Nina Kastner, Núria Nadal-Gratacós, Selina Hemmer et al.
correction
A correction notice clarifies that two errors in the original paper do not affect the accuracy of the results, interpretations, or conclusions. The first correction addresses a presentation issue in Table 1, confirming the data are correct. The second correction clarifies that thigmotaxis, a measure of anxiety-like behavior, was evaluated in rats given SDA or SDMA compounds. Compared to saline, only the 10 mg/kg dose of SDA significantly increased thigmotaxis, meaning the rats spent less time in the center of the arena.
ACS Chemical Neuroscience
December 2, 2025
Nina Kastner, Núria Nadal‐gratacós, Selina Hemmer et al.
Replacing the 1,3-benzodioxole group in MDMA (ecstasy) with a 1,3-benzoxathiole yields two analogues, SDA and SDMA, that interact with monoamine transporters similarly to MDMA but with key differences. SDA and SDMA inhibit dopamine and norepinephrine transporters more potently than MDMA and act as partial releasers at serotonin and dopamine transporters. Metabolism studies show SDA and SDMA are cleared faster, while MDMA and MDA degrade only weakly. In mice, SDMA does not produce rewarding effects, unlike MDMA, and SDA only shows a preference for the drug-paired compartment at the lowest dose. SDMA shares similar locomotor and hyperthermic profiles with MDMA, whereas SDA induces increased hyperlocomotion and more sustained hyperthermia. SDMA may be a safer candidate for further study.
Journal of Medicinal Chemistry
September 25, 2025
Tyler G. Fenske, J. M. T. Mckee, Natalie G. Cavalco et al.
Selectivity for the 5-HT2A receptor over the closely related 5-HT2C receptor can be achieved by targeting residue L1232.53 in transmembrane 2 of the extended binding pocket through increasing steric aliphatic bulk on the α-methylene group of the N-benzyl chemical scaffold. This selectivity was confirmed across 5-HT2C RNA editing isoforms, TM2 reciprocal mutants, and mouse orthologs, producing the most highly selective 5-HT2A agonists to date. Using structure–activity relationships, molecular docking, and mouse head-twitch response assays, the work demonstrates that such agonists can be rationally designed to improve target engagement, advancing the study of the neurobiological mechanisms of psychedelic effects.
UNC Libraries
October 31, 2020
Adam Pigott, Bryan L. Roth, Xi‐ping Huang et al.
Replacing the ethylamine side chain of the psychedelic compounds DOI and DOB with a cyclopropylamine group produced new molecules that bind strongly to 5-HT2 family serotonin receptors. The most potent version had the (−)-(1R,2S)-configuration. However, these cyclopropane analogs also showed increased affinity for other serotonin receptor subtypes beyond 5-HT2A and 5-HT2B, making them less selective than the original compounds. At appropriate doses, they may serve as research tools for studying 5-HT2 receptor function, but their reduced selectivity for 5-HT2A receptors must be considered.