Depressive DisordersMedicinal Chemistry & Drug Development

Psychedelics promote neuroplasticity through the activation of intracellular 5-HT2A receptors

The study shows that psychedelics promote cortical neuroplasticity by selectively activating intracellular 5-HT2A receptors rather than surface receptors, explaining why serotonin does not elicit the same growth effects. This identifies location-biased 5-HT2A signalling as a therapeutic target and raises the possibility that serotonin may not be the endogenous ligand for intracellular 5-HT2ARs.

Authors

  • David Olson
  • John McCorvy
  • Lindsay Cameron

Published

Science
individual Study

Abstract

Decreased dendritic spine density in the cortex is a hallmark of several neuropsychiatric diseases, and the ability to promote cortical neuron growth has been hypothesized to underlie the rapid and sustained therapeutic effects of psychedelics. Activation of 5-hydroxytryptamine (serotonin) 2A receptors (5-HT2ARs) is essential for psychedelic-induced cortical plasticity, but it is currently unclear why some 5-HT2AR agonists promote neuroplasticity, whereas others do not. We used molecular and genetic tools to demonstrate that intracellular 5-HT2ARs mediate the plasticity-promoting properties of psychedelics; these results explain why serotonin does not engage similar plasticity mechanisms. This work emphasizes the role of location bias in 5-HT2AR signaling, identifies intracellular 5-HT2ARs as a therapeutic target, and raises the intriguing possibility that serotonin might not be the endogenous ligand for intracellular 5-HT2ARs in the cortex.

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Research Summary of 'Psychedelics promote neuroplasticity through the activation of intracellular 5-HT2A receptors'

Introduction

Dysregulation of the cortex, including reduced dendritic arbor complexity and lower dendritic spine density, is implicated in several neuropsychiatric disorders and is a target for therapeutics that promote structural plasticity. Psychoplastogens such as ketamine and serotonergic psychedelics produce rapid and sustained increases in cortical structural and functional plasticity; for psychedelics this effect requires activation of 5-hydroxytryptamine 2A receptors (5-HT2ARs). However, a puzzling observation is that some 5-HT2AR agonists promote cortical neuroplasticity while others, including endogenous serotonin, do not, despite serotonin being a potent, balanced 5-HT2AR agonist in canonical signalling assays. The physicochemical differences between ligands led the investigators to consider location bias — the idea that receptor signalling differs depending on whether ligands access plasma-membrane versus intracellular receptor pools — as a possible explanation. Vargas and colleagues set out to test whether activation of an intracellular population of 5-HT2ARs is necessary for psychedelics to induce cortical structural plasticity and related antidepressant-like behavioural responses. To do so they combined in vivo pharmacology and genetics (including 5-HT2AR knockout mice and viral expression of transporters), in vitro neuronal culture assays and structure–activity studies of tryptamine analogues, fluorescence- and biophysical-reporter assays of receptor conformation and signalling, subcellular localisation experiments, and chemical modification of ligands to alter membrane permeability.

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