1. Use of the head-twitch response to investigate the structure–activity relationships of 4-thio-substituted 2,5-dimethoxyphenylalkylamines
- Author
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Halberstadt, Adam L, Luethi, Dino, Hoener, Marius C, Trachsel, Daniel, Brandt, Simon D, and Liechti, Matthias E
- Subjects
Biological Psychology ,Psychology ,5.1 Pharmaceuticals ,Development of treatments and therapeutic interventions ,Mice ,Male ,Humans ,Animals ,Hallucinogens ,Receptor ,Serotonin ,5-HT2A ,Artificial Intelligence ,Serotonin ,Mice ,Inbred C57BL ,Structure-Activity Relationship ,Psychedelic ,Hallucinogen ,5-HT2A receptor ,Head-twitch response ,Phenethylamine ,Medical and Health Sciences ,Psychology and Cognitive Sciences ,Psychiatry ,Biological psychology - Abstract
Rationale4-Thio-substituted phenylalkylamines such as 2,5-dimethoxy-4-ethylthiophenethylamine (2C-T-2) and 2,5-dimethoxy-4-n-propylthiophenethylamine (2C-T-7) produce psychedelic effects in humans and have been distributed as recreational drugs.ObjectivesThe present studies were conducted to examine the structure-activity relationships (SAR) of a series of 4-thio-substituted phenylalkylamines using the head twitch response (HTR), a 5-HT2A receptor-mediated behavior induced by psychedelic drugs in mice. The HTR is commonly used as a behavioral proxy in rodents for human psychedelic effects and can be used to discriminate hallucinogenic and non-hallucinogenic 5-HT2A agonists.MethodsHTR dose-response studies with twelve different 4-thio-substituted phenylalkylamines were conducted in male C57BL/6 J mice. To detect the HTR, head movement was recorded electronically using a magnetometer coil and then head twitches were identified in the recordings using a validated method based on artificial intelligence.Results2C-T, the parent compound of this series, had relatively low potency in the HTR paradigm, but adding an α-methyl group increased potency fivefold. Potency was also increased when the 4-methylthio group was extended by one to three methylene units. Fluorination of the 4-position alkylthio chain, however, was detrimental for activity, as was the presence of a 4-allylthio substituent versus a propylthio group. 2C-T analogs containing a 4-benzylthio group showed little or no effect in the HTR paradigm, which is consistent with evidence that bulky 4-substituents can dampen agonist efficacy at the 5-HT2A receptor. Binding and functional studies confirmed that the compounds have nanomolar affinity for 5-HT2 receptor subtypes and act as partial agonists at 5-HT2A.ConclusionsIn general, there were close parallels between the HTR data and the known SAR governing activity of phenylalkylamines at the 5-HT2A receptor. These findings further support the classification of 2C-T compounds as psychedelic drugs.
- Published
- 2023