Identification of 5-HT 2A Receptor Signaling Pathways Responsible for Psychedelic Potential

• Published in: bioRxiv : the preprint server for biology
• Main Authors: Wallach, Jason, Cao, Andrew B, Calkins, Maggie M, Heim, Andrew J, Lanham, Janelle K, Bonniwell, Emma M, Hennessey, Joseph J, Bock, Hailey A, Anderson, Emilie I, Sherwood, Alexander M, Morris, Hamilton, de Klein, Robbin, Klein, Adam K, Cuccurazzu, Bruna, Gamrat, James, Fannana, Tilka, Zauhar, Randy, Halberstadt, Adam L, McCorvy, John D
• Format: Journal Article
• Language: English
• Published: United States 31.07.2023

Serotonergic psychedelics possess considerable therapeutic potential. Although 5-HT receptor activation mediates psychedelic effects, prototypical psychedelics activate both 5-HT -Gq/11 and β-arrestin2 signaling, making their respective roles unclear. To elucidate this, we developed a series of 5-HT -selective ligands with varying Gq efficacies, including β-arrestin-biased ligands. We show that 5-HT -Gq but not 5-HT -β-arrestin2 efficacy predicts psychedelic potential, assessed using head-twitch response (HTR) magnitude in male mice. We further show that disrupting Gq-PLC signaling attenuates the HTR and a threshold level of Gq activation is required to induce psychedelic-like effects, consistent with the fact that certain 5-HT partial agonists (e.g., lisuride) are non-psychedelic. Understanding the role of 5-HT -Gq efficacy in psychedelic-like psychopharmacology permits rational development of non-psychedelic 5-HT agonists. We also demonstrate that β-arrestin-biased 5-HT receptor agonists induce receptor downregulation and tachyphylaxis, and have an anti-psychotic-like behavioral profile. Overall, 5-HT receptor signaling can be fine-tuned to generate ligands with properties distinct from classical psychedelics.