mGlu2 and mGlu3 Negative Allosteric Modulators Divergently Enhance Thalamocortical Transmission and Exert Rapid Antidepressant-like Effects

Neuron. 2020 Jan 8;105(1):46-59.e3. doi: 10.1016/j.neuron.2019.09.044. Epub 2019 Nov 14.

Abstract

Non-selective antagonists of metabotropic glutamate receptor subtypes 2 (mGlu2) and 3 (mGlu3) exert rapid antidepressant-like effects by enhancing prefrontal cortex (PFC) glutamate transmission; however, the receptor subtype contributions and underlying mechanisms remain unclear. Here, we leveraged newly developed negative allosteric modulators (NAMs), transgenic mice, and viral-assisted optogenetics to test the hypothesis that selective inhibition of mGlu2 or mGlu3 potentiates PFC excitatory transmission and confers antidepressant efficacy in preclinical models. We found that systemic treatment with an mGlu2 or mGlu3 NAM rapidly activated biophysically unique PFC pyramidal cell ensembles. Mechanistic studies revealed that mGlu2 and mGlu3 NAMs enhance thalamocortical transmission and inhibit long-term depression by mechanistically distinct presynaptic and postsynaptic actions. Consistent with these actions, systemic treatment with either NAM decreased passive coping and reversed anhedonia in two independent chronic stress models, suggesting that both mGlu2 and mGlu3 NAMs induce antidepressant-like effects through related but divergent mechanisms of action.

Keywords: anhedonia; antidepressant; chronic stress; mGlu receptor; major depressive disorder; metabotropic glutamate receptor; neuronal ensembles; prefrontal cortex; synaptic plasticity; thalamus.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Psychological / drug effects
  • Allosteric Regulation / physiology*
  • Anhedonia / drug effects
  • Animals
  • Antidepressive Agents / pharmacology
  • Behavior, Animal / drug effects
  • Cerebral Cortex / metabolism
  • Cerebral Cortex / physiology*
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Glutamic Acid / metabolism
  • Long-Term Synaptic Depression / drug effects
  • Male
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Neural Pathways / physiology
  • Neuronal Plasticity / physiology
  • Optogenetics
  • Prefrontal Cortex / metabolism
  • Prefrontal Cortex / physiology
  • Proto-Oncogene Proteins c-fos / genetics
  • Proto-Oncogene Proteins c-fos / metabolism
  • Pyramidal Cells / physiology
  • Receptors, Metabotropic Glutamate / antagonists & inhibitors*
  • Thalamus / metabolism
  • Thalamus / physiology*

Substances

  • Antidepressive Agents
  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • Proto-Oncogene Proteins c-fos
  • Receptors, Metabotropic Glutamate
  • metabotropic glutamate receptor 2
  • metabotropic glutamate receptor 3
  • Glutamic Acid