Neuropharmacology
May 1, 2020
Adam L Halberstadt, Muhammad Chatha, Adam K Klein et al.
274 citations
Serotonergic hallucinogens like LSD cause head twitches in rodents through 5-HT2A receptor activation. This study tested whether the potency of hallucinogens in the mouse head-twitch response (HTR) paradigm correlates with their potencies in rats and humans. Dose-response experiments with phenylalkylamine and tryptamine hallucinogens in C57BL/6J mice expanded HTR potency data to 41 compounds. For 36 agents with human data, a strong positive correlation (r = 0.9448) was found between mouse HTR potencies and human hallucinogenic potencies. HTR potencies also correlated with drug discrimination ED50 values in rats trained with LSD (r = 0.9484, n = 16) or 2,5-dimethoxy-4-methylamphetamine (r = 0.9564, n = 21). These three behavioral effects show consistent potencies linked to 5-HT2A receptor activation, supporting the HTR assay as a predictive preclinical model for hallucinogen potency in humans.
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.
Neuropharmacology
November 19, 2019
Adam L. Halberstadt, Muhammad Chatha, Adam K. Klein et al.
37 citations
Psilocybin, a naturally occurring hallucinogen, significantly enhances serotonin receptor activity, leading to profound psychological effects. In a sample of 100 participants, 75% reported lasting positive changes in mood and outlook after a single dose. The pharmacology of psilocybin shows it acts as an agonist at serotonin receptors, similar to lysergic acid diethylamide (LSD). These findings highlight the potential of psychedelics in therapeutic settings, driven by intricate biochemical interactions and chemical synthesis of alkaloids that influence brain chemistry and behavior.
Journal of Psychopharmacology
February 21, 2019
Adam L. Halberstadt, Muhammad Chatha, Stephen J. Chapman et al.
25 citations
In mice, the hallucinogenic compound mescaline and several of its chemical analogs produce a distinctive head-twitch response that depends on activation of the 5-HT2A receptor. Adding a methyl group to mescaline (making TMA) doubled its potency, and replacing the 4-methoxy group with larger ethoxy or propoxy groups also increased potency for both mescaline and TMA. However, for a different set of isomers (TMA-2 and its analogs), changing the 4-alkoxy group did not alter potency, even though TMA-2 itself was twice as potent as mescaline. These potency patterns in mice closely match known human hallucinogenic data and show that different substitution patterns on the phenyl ring produce distinct structure-activity relationships.
Psychopharmacology
February 14, 2019
Adam L. Halberstadt, Landon M. Klein, Muhammad Chatha et al.
25 citations
The lysergamide ECPLA, a close structural analog of LSD, binds with high affinity to serotonin, adrenergic, and dopamine receptors, and acts as a potent agonist at the 5-HT₂A receptor, which mediates psychedelic effects. In mice, ECPLA induced head twitches with an ED₅₀ of 317.2 nmol/kg, about 40% as potent as LSD. Two other analogs, LAMPA (ED₅₀ = 358.3 nmol/kg) and MIPLA (ED₅₀ = 421.7 nmol/kg), showed similar or slightly lower potency. These findings indicate that ECPLA, MIPLA, and LAMPA share pharmacological properties with LSD and other lysergamide hallucinogens.
Neuropharmacology
January 1, 2019
Adam L Halberstadt, Muhammad Chatha, Alexander Stratford et al.
25 citations
Rigid analogs of phenylalkylamine hallucinogens, such as 2C-B-FLY and Bromo-DragonFLY (DOB-DFLY), have emerged as recreational drugs. In mice, the head twitch response—a behavior mediated by the 5-HT2A receptor—was used to compare potencies. DOB (ED50 = 0.75 μmol/kg) and 2C-B (ED50 = 2.43 μmol/kg) induced the response. Benzodifurans DOB-DFLY (ED50 = 0.20 μmol/kg) and 2C-B-DFLY (ED50 = 1.07 μmol/kg) showed significantly higher potency than their non-rigid counterparts. Tetrahydrobenzodifurans DOB-FLY (ED50 = 0.67 μmol/kg) and 2C-B-FLY (ED50 = 1.79 μmol/kg) were approximately equipotent. Three novel tetrahydrobenzodifurans were active but had relatively low potency.
Psychopharmacology
February 14, 2019
Adam L. Halberstadt, Jochem V. F. Zee, Muhammad Chatha et al.
21 citations
Chronic treatment with an mGlu2/3 receptor agonist, LY379268, attenuated the head-twitch response (HTR) induced by the selective 5-HT2A agonist 25CN-NBOH in mice, even when tested 48 hours after the last dose. Acute LY379268 also reduced the HTR by about 50%. The HTR was completely blocked by a 5-HT2A antagonist but not by a 5-HT2C antagonist. In locomotor tests, acute LY379268 reduced PCP-induced hyperactivity in mice that had received chronic vehicle treatment, but only a trend for an interaction was seen in the chronic LY379268 group. These results support a functional interaction between mGlu2/3 and 5-HT2A receptors in modulating behavioral responses to 5-HT2A activation.
ACS chemical neuroscience
May 6, 2020
Emil Marcher-Rørsted, Adam L Halberstadt, Adam K Klein et al.
20 citations
The 2,5-dimethoxy motif found in many phenethylamine psychedelics has been considered essential for activating the serotonin 2A receptor (5-HT2AR). This study synthesized derivatives of 2C-B and DOB lacking either the 2- or 5-methoxy group and tested them in binding and functional assays at 5-HT2AR and 5-HT2CR, as well as in mice for head-twitch response, a behavioral proxy for psychedelic activity. Removing either methoxy group caused a modest drop in binding affinity and functional potency at both receptors, with larger effects from removing the 2-methoxy group. However, in mice, removal of either group drastically reduced head-twitch response. Thus, the 2,5-dimethoxy motif is important for in vivo potency, but this does not correlate with in vitro receptor affinity or potency.