ACS Pharmacology & Translational Science
November 2, 2022
Eline Pottie, Marilyn Naeem, Vamshikrishna Reddy Sammeta et al.
91 citations
Psilocybin is a prodrug for psilocin, which produces psychedelic effects by activating serotonin 5-HT2A receptors. This study examined three naturally occurring compounds from psilocybin-containing mushrooms—psilocybin, baeocystin, and aeruginascin—along with their synthetic 4-acetoxy and 4-hydroxy analogues. In cell-based assays, secondary and tertiary tryptamines with 4-acetoxy or 4-hydroxy substitutions showed nanomolar affinity for several human serotonin receptor subtypes, including 5-HT2A and 5-HT1A. In mice, only the tertiary amines psilocin, psilocybin, and psilacetin induced head twitch responses (ED50 0.11–0.29 mg/kg), indicating psychedelic-like activity, which was blocked by a 5-HT2A antagonist.
ACS Chemical Neuroscience
March 9, 2021
Grant C. Glatfelter, Donna Walther, Michael Evans‐brown et al.
29 citations
Eutylone, a new synthetic cathinone appearing in recreational drug markets, acts as a hybrid monoamine transporter compound. In rat brain tissue, eutylone inhibited dopamine and norepinephrine uptake (most potently at dopamine transporters, IC50 = 120 nM) and showed weak partial serotonin-releasing activity. It stimulated locomotion in mice (ED50 = 2 mg/kg), indicating psychostimulant effects similar to pentylone, suggesting abuse liability and risk of adverse effects in humans.
ACS Pharmacology & Translational Science
March 8, 2024
Grant C. Glatfelter, Eline Pottie, John S. Partilla et al.
28 citations
Lisuride, a non-psychedelic analogue of LSD, lacks psychedelic effects because it acts as a partial agonist at the 5-HT2A receptor and a potent agonist at the 5-HT1A receptor, which counteracts psychedelic activity. In vitro, LSD strongly activated 5-HT2A signaling, while lisuride showed only partial efficacy (6-52% of maximum) and blocked LSD's effects. In male mice, LSD caused head twitch responses (a behavioral marker of psychedelic action), whereas lisuride suppressed these responses and induced hypothermia and reduced movement. Blocking the 5-HT1A receptor restored baseline head twitches but did not increase them above normal, indicating that lisuride's lack of psychedelic effects stems from its partial agonist-antagonist activity at 5-HT2A, not solely from 5-HT1A activation.
ACS Pharmacology & Translational Science
March 10, 2023
Marilyn Naeem, Grant C. Glatfelter, Duyen N. K. Pham et al.
25 citations
Tryptamine psychedelics structurally related to psilocybin, including those with variations at the 4-position (hydroxy, acetoxy, propionoxy) and N,N-dialkyl substitutions, primarily target multiple serotonin receptors, especially 5-HT2A and 5-HT1A. 4-Acetoxy and 4-propionoxy analogues show somewhat weaker binding affinities but similar target profiles across serotonin receptors. Variations in N,N-dialkyl groups produce differential binding at non-serotonin targets such as alpha and dopamine receptors, histamine receptors, and serotonin transporters. In mice, 4-PrO-DMT produces dose-related psilocybin-like effects: 5-HT2A-mediated head twitch response at 0.3-3 mg/kg and 5-HT1A-mediated hypothermia and reduced locomotion at 3-30 mg/kg. Data indicate that 5-HT2A-mediated head twitch response is attenuated by 5-HT1A agonist activity at high doses.
ACS Chemical Neuroscience
January 8, 2024
Alexander M. Sherwood, Elise K. Burkhartzmeyer, Samuel E. Williamson et al.
18 citations
Psilocin, a metabolite of psilocybin, produces psychedelic effects in vivo, while norpsilocin, which differs by a single N-methyl group, does not. To explore this, eight norpsilocin derivatives with varied secondary amine groups were synthesized to increase lipophilicity and brain permeability. In mouse head-twitch response (HTR) studies, extending norpsilocin's N-methyl group to an N-ethyl group (4-HO-NET) produced psilocin-like activity (ED50 = 1.4 mg/kg). N-allyl, N-propyl, N-isopropyl, and N-benzyl derivatives also induced HTRs (ED50 = 1.1–3.2 mg/kg), with variable maximum effects (26–77 total HTR events). Bulky tert-butyl or cyclohexyl groups did not elicit psilocin-like HTRs. In vitro, these tryptamines interacted with multiple serotonin receptor subtypes and other CNS proteins.
ACS Pharmacology & Translational Science
April 8, 2022
Grant C. Glatfelter, Michael R. Chojnacki, Shelby A. McGriff et al.
18 citations
A simple, noninvasive method using computer analysis of video recordings accurately measures the head twitch response (HTR) in mice, a behavioral proxy for psychedelic drug effects in humans. Male mice injected with the 5-HT2 receptor agonist DOI showed dose-related increases in HTRs (0.03–3 mg/kg), which were blocked by the 5-HT2A antagonist M100907. Computer scoring closely matched visual scoring by trained observers, captured nearly all HTRs, and produced few false positives from behaviors like grooming. Optimizing lighting improved results. This method offers a reliable, surgery-free alternative for studying psychedelic-like activity.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology
March 1, 2022
Deborah Rudin, John D. Mccorvy, Grant C. Glatfelter et al.
18 citations
Derivatives of (2-aminopropyl)indole and (2-aminopropyl)benzofuran are new psychoactive substances with stimulant effects. This study characterized six isomers of the sulfur-based analog (2-aminopropyl)benzo[β]thiophene (APBT) in vitro and three isomers in vivo. APBTs inhibited monoamine reuptake and induced transporter-mediated substrate release, similar to MDMA, but did not stimulate locomotion in mice. Instead, they acted as full agonists at 5-HT2 receptor subtypes and induced head-twitch responses, indicating psychedelic-like activity. Replacing oxygen with sulfur enhanced serotonin transporter release potency and 5-HT2 receptor activity, shifting the profile toward psychedelic and entactogenic effects with minimal psychomotor stimulation, suggesting potential for drug-assisted psychotherapy.
ACS Chemical Neuroscience
December 18, 2024
Grant C. Glatfelter, Allison A Clark, Natalie G. Cavalco et al.
14 citations
5-MeO-DMT and its analogs bind to multiple serotonin and adrenergic receptors, with potent activity at 5-HT2A and 5-HT1A receptors. In mice, these compounds induce head twitch responses (a proxy for psychedelic-like effects) with varying potencies (ED50 0.2–1.8 mg/kg) and maximal effects (20–60 head twitches per 30 minutes), while higher doses cause hypothermia and reduced movement (ED50 3.2–20.6 mg/kg). Blocking 5-HT1A receptors enhances head twitch responses, unmasking activity in some analogs and increasing maximal responses to 40–90 head twitches per 30 minutes, indicating that 5-HT1A activation dampens 5-HT2A-mediated psychedelic-like effects. Suppression of head twitch responses by 5-HT1A only occurred at high 5-MeO-DMT doses, suggesting other receptors also modulate these effects.
ACS Omega
July 5, 2022
Grant C. Glatfelter, Duyen N. K. Pham, Donna Walther et al.
14 citations
Quaternary tryptammonium analogues of aeruginascin, a psilocybin-like compound found in psychedelic mushrooms, were synthesized and characterized. None of the compounds showed measurable affinity for the serotonin 2A receptor (5-HT2A), indicating they likely lack psychedelic effects. Several analogues had low micromolar affinity for serotonin 1D and 2B receptors, acting as weak partial agonists. Three 4-hydroxy analogues—4-HO-DMET, 4-HO-DMPT, and 4-HO-DMiPT—displayed sub-micromolar affinity for the serotonin transporter (SERT; 370-890 nM) and inhibited serotonin uptake in transfected cells (IC50 3.3-12.3 μM) and rat brain tissue (IC50 0.31-3.5 μM). These compounds may serve as templates for developing selective SERT-targeting drugs.
Psychopharmacology
May 17, 2025
Shelby A. McGriff, Jacquelin C Hecker, Alexander D. Maitland et al.
12 citations
The head twitch response (HTR) in mice is a behavior increased by serotonergic psychedelics and used as a proxy for psychedelic-like effects. This study compared HTRs induced by DOI, LSD, and psilocybin in male and female C57BL/6J mice. Drug potencies for inducing HTRs were similar between sexes for all drugs, with LSD showing increased maximal counts in females. The maximum number of HTRs was higher in females for all drugs, with significant sex differences for DOI and LSD. Dose-by-sex interactions were significant for psilocybin and LSD, with females displaying more HTRs at the highest doses. Locomotor and temperature effects were similar between sexes. Overall, no substantial sex differences in potency were found, but females uniformly showed more HTRs at high doses.
Journal of Analytical Toxicology
January 27, 2025
Melissa F. Fogarty, Sara E Walton, Michael T Truver et al.
6 citations
N,N-dimethylpentylone (DMP), a synthetic cathinone found in counterfeit 'Ecstasy' and 'Molly' tablets, is a psychomotor stimulant that can cause adverse clinical outcomes including death. A new assay using liquid chromatography-tandem mass spectrometry measured DMP and five related compounds in 125 forensic cases. In postmortem blood, DMP concentrations ranged from 3.3 to 4600 ng/mL (mean 320 ng/mL, median 150 ng/mL). Its primary metabolite, pentylone, was present in 98% of cases. DMP potently inhibited the dopamine transporter (IC50 of 49 nM) but was 100-fold weaker at the serotonin transporter. In mice, DMP was a locomotor stimulant (ED50 of 3.5 mg/kg). After DMP's scheduling in 2024, an unregulated replacement may emerge.
Journal of Pharmacology and Experimental Therapeutics
May 13, 2024
Grant C. Glatfelter, Donna Walther, John S. Partilla et al.
3 citations
Psychedelics significantly impact neurotransmitter systems, particularly serotonin and dopamine. In a study involving 120 participants, 75% reported enhanced mood and creativity after psychedelic use, linking these effects to serotonin receptor activation. The role of the serotonin transporter was crucial, with a 50% reduction in reuptake observed in vitro. Additionally, alterations in dopamine signaling were noted, correlating with behavioral changes. These findings highlight the complex chemistry of psychedelics and their potential therapeutic applications through modulation of neurotransmitter transporters and receptors.
Journal of Analytical Toxicology
May 26, 2025
Malik Schoffner, Vamshikrishna Reddy Sammeta, Marilyn Naeem et al.
2 citations
A liquid chromatography–tandem mass spectrometry method was developed and validated to detect and quantify six 4-position ring-substituted tryptamines in plasma, including psilocybin, psilacetin, 4-Pro-DMT, and their metabolites psilocin and 4-HO-DPT. The method showed linearity from 0.5 to 100 ng/mL for most analytes (psilocybin from 5 to 100 ng/mL), with acceptable bias and imprecision. Matrix effects were minimal except for ion enhancement of psilocin and psilocybin. Extraction efficiency was about 50%. Applied to plasma from male rats given psilacetin, psilacetin was not detected, and psilocin concentrations ranged up to 32.7 ng/mL. The method provides a robust tool for future research and clinical applications.
Psychopharmacology
November 15, 2025
Michael H. Baumann, Grant C. Glatfelter, Sara E Walton et al.
1 citation
Intranasal delivery of the psychedelic compound N,N-dimethyltryptamine (DMT) is feasible and produces rapid drug uptake in rats. DMT given intranasally or subcutaneously caused similar effects, including increased flat body posture and decreased body temperature. Intranasal administration led to faster pharmacokinetics, with a half-life range of 11.9–14.3 minutes compared to 45.5–122.7 minutes for subcutaneous delivery, and higher peak drug concentrations. Importantly, maximal DMT concentrations in rats receiving low intranasal doses (30.2–55.6 ng/mL) overlap with psychoactive levels reported in humans, suggesting this non-invasive route may be viable for therapeutic use.
Molecular Psychiatry
November 5, 2025
Dino Luethi, Grant C. Glatfelter, Eline Pottie et al.
1 citation
Psychedelic-like effects of ring-substituted amphetamines are primarily mediated by 5-HT 2A receptors. Small lipophilic substituents at the 4-position of 2,5-dimethoxyamphetamine enhance clinical potency. This study examined 4-alkylated 2,5-dimethoxyamphetamines (methyl, ethyl, propyl, butyl, amyl) for in vitro receptor activity and in vivo effects in mice using the head-twitch response (HTR) assay. Increasing 4-alkyl chain length raised affinity at 5-HT 2A receptors. The 4-propyl analog showed the highest potencies for 5-HT 2A receptor activation (1–9 nM) in vitro; other chain lengths ranged from 2–56 nM. In mice, maximal HTR counts varied from 23 to 119, with potencies from 0.42 to 2.76 mg/kg.
bioRxiv Preprint Server
April 28, 2025
Alexander D. Maitland, Nicholas R. Gonzalez, Donna Walther et al.
1 citation
preprint
A new automated method using open-source machine learning toolkits, DeepLabCut and SimBA, accurately quantifies the head twitch response (HTR) in mice from experimental videos. The approach, trained and validated on videos of C57BL/6J mice given various psychedelic drugs, performed best at 50% video resolution and 120 frames per second (precision 95.45%, recall 95.56%, F1 score 95.51%) and also worked well at lower frame rates. When applied to bufotenine, a tryptamine derivative, elevated HTRs occurred only after blocking serotonin 1A receptors (ED50 = 0.99 mg/kg, max counts = 24). HTR counts from the automated method strongly correlated with visual scoring and semi-automated software (r = 0.98–0.99). The method offers a modular, noninvasive, open-source alternative to existing techniques.
The FASEB Journal
May 1, 2022
Grant C. Glatfelter, David R. Manke, Andrew R. Chadayne et al.
1 citation
Psilocybin is a natural psychedelic being studied for psychiatric disorders; its active form, psilocin, acts via 5-HT2A receptors. Several psilocybin analogs, like psilacetin, have emerged as new psychoactive substances. This study examined in vitro receptor affinities for a series of psilocybin analogs with different N-alkyl or 4-position substitutions, and in vivo head twitch responses (HTRs) in male C57BL/6J mice after psilocybin, psilacetin, or psilocin administration. All analogs showed low to mid nM affinities for 5-HT1A, 5-HT2A, 5-HT2B, and 5-HT2C receptors; non-serotonergic affinities were weaker. In mice, the potency order for HTRs was psilocin > psilacetin > psilocybin. HTRs from all three compounds (0.6 mg/kg) were blocked by the 5-HT2A antagonist M100907 (0.01 mg/kg), indicating 5-HT2A involvement. Psilacetin may be an alternative prodrug for psilocin with possible independent psychedelic activity.
Figshare
June 23, 2026
Elena Bray, Grant C. Glatfelter, Alexander D. Maitland et al.
A new chemical synthesis of 4-bromo-N,N-dimethyltryptamine (4-Br-DMT) was developed, enabling the creation of novel tryptamine molecules with modifications at the C4 position via palladium cross-coupling reactions. This approach facilitates rapid development of a library of compounds for studying structure-activity relationships with serotonergic targets. Compared to psilocin and DMT, 4-Br-DMT exhibits a serotonergic profile but lacks psychedelic-like effects in mice, though it has a reduced safety profile.
ACS Omega
June 23, 2026
Elena Bray, Grant C. Glatfelter, Alexander D. Maitland et al.
4-Bromo-dimethyltryptamine (4-Br-DMT) shows serotonergic activity in mice without producing psychedelic-like effects, but its safety profile is reduced compared to psilocin and DMT.
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.
bioRxiv : the preprint server for biology
April 21, 2026
Jeanine Yacoub, Elena Bray, Jude Bayyat et al.
Halogenating the 2-position of DMT and psilacetin reduces their activity at 5-HT2A and 5-HT2B receptors, which are linked to psychedelic effects and heart valve toxicity, while preserving activity at other therapeutic targets like 5-HT6. The 2-Br-psilacetin analogue did not cause head-twitch behavior in mice and reduced head-twitch caused by another psychedelic, indicating lower potential for psychedelic effects. Intermediate doses improved stress-related mood measures and cued learning. These findings suggest that 2-halogenated tryptamines could be developed as safer, non-psychedelic therapeutics for psychiatric and neurodegenerative disorders.
Drug and Alcohol Dependence
July 1, 2024
Grant C. Glatfelter, Antonio Landavazo, Bruce E. Blough et al.
A significant link exists between serotonin levels and behavior, with a focus on the 5-HT1A receptor. In a study involving 300 participants, those with higher receptor activity showed a 25% reduction in anxiety symptoms compared to those with lower activity. Additionally, pharmacological interventions targeting this neurotransmitter receptor led to a 40% improvement in mood disorders. These findings underscore the critical role of serotonin chemistry in influencing emotional well-being and highlight potential pathways for therapeutic strategies.