Investigation of the Structure–Activity Relationships of Psilocybin Analogues

Abstract

The 5-HT2A receptor is thought to be the primary target for psilocybin (4-phosphoryloxy-N,N-dimethyltryptamine) and other serotonergic hallucinogens (psychedelic drugs). Although a large amount of experimental work has been conducted to characterize the pharmacology of psilocybin and its dephosphorylated metabolite psilocin (4-hydroxy-N,N-dimethyltryptamine), there has been little systematic investigation of the structure–activity relationships (SAR) of 4-substituted tryptamine derivatives. In addition, structural analogs of psilocybin containing a 4-acetoxy group, such as 4-acetoxy-N,N-dimethyltryptamine (4-AcO-DMT), have appeared as new designer drugs, but almost nothing is known about their pharmacological effects. To address the gap of information, studies were conducted with 17 tryptamines containing a variety of symmetrical and asymmetrical N,N-dialkyl substituents and either a 4-hydroxy or 4-acetoxy group. Calcium mobilization assays were conducted to assess functional activity at human and mouse 5-HT2 subtypes. Head-twitch response (HTR) studies were conducted in C57BL/6J mice to assess 5-HT2A activation in vivo. All of the compounds acted as full or partial agonists at 5-HT2 subtypes, displaying similar potencies at 5-HT2A and 5-HT2B receptors, but some tryptamines with bulkier N-alkyl groups had lower potency at 5-HT2C receptors and higher 5-HT2B receptor efficacy. In addition, O-acetylation reduced the in vitro 5-HT2A potency of 4-hydroxy-N,N-dialkyltryptamines by about 10- to 20-fold but did not alter agonist efficacy. All of the compounds induce head twitches in mice, consistent with an LSD-like behavioral profile. In contrast to the functional data, acetylation of the 4-hydroxy group had little effect on HTR potency, suggesting that O-acetylated tryptamines may be deacetylated in vivo, acting as prodrugs. In summary, the tryptamine derivatives have psilocybin-like pharmacological properties, supporting their classification as psychedelic drugs.

Harnessing psilocybin: antidepressant-like behavioral and synaptic actions of psilocybin are independent of 5-HT2R activation in mice

“…Ketanserin was administered 60 min prior to injection with either vehicle control or psilocybin, consistent with previous studies of ketanserin's ability to block hallucinogenic behavioral responses in humans (8) and rats (18). Psilocybin injections were given at 1 mg/kg and ketanserin at 2 mg/kg, consistent with previous rodent studies (13,38), or equivalent volumes of saline. Each experimental animal received two injections to control for any effects of injection or handling.…”

In vitro assays for the functional characterization of (psychedelic) substances at the serotonin receptor 5‐HT2AR

“…Other dyes, such as fluo‐3 and fluo‐4, do not have this shift in spectrum when binding Ca 2+ , but can be used for the detection of intracellular Ca 2+ concentrations because their fluorescence intensity increases in the Ca 2+ bound state. Ca 2+ mobilization is then estimated via the increase in fluorescence intensity after excitation at a single wavelength (Arunotayanun et al, 2013; Blough et al, 2014; Brandt et al, 2018; Cussac et al, 2008; Elmore et al, 2018; Flanagan et al, 2021; Halberstadt et al, 2019, 2020; Jensen et al, 2017; Jerman et al, 2001; Klein et al, 2021; Kolaczynska et al, 2019; Leth‐Petersen et al, 2016; Luethi et al, 2018, 2019; Marcher‐Rorsted et al, 2020; Minta et al, 1989; Nichols et al, 2015; Ray, 2010; Rickli et al, 2015; Rickli, Luethi, et al, 2015; Sullivan et al, 1999).…”

CFH Loss in Human RPE Cells Leads to Inflammation and Complement System Dysregulation via the NF-κB Pathway

“…Interestingly, in the cfh −/−mouse model, also other organs are pathologically affected by excessive inflammation and immune cell infiltration, such as the kidney [39] and the liver [40]. For example, cfh −/− mice face a spontaneous appearance of hepatocellular carcinomas with a clear transcriptomic signature for cytokine and chemokine signaling pathways [41]. Similarly, the phenotype of mature iPSC-RPE cells carrying the CFH Y402H AMD high-risk variant is characterized by the upregulation of several inflammatory cytokines, as IL6 [42,43] and C3b deposition [44].…”