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Welsch L, Colantonio E, Frison M, Johnson DA, McClain SP, Mathis V, Banghart MR, Ben Hamida S, Darcq E, Kieffer BL. Mu Opioid Receptor-Expressing Neurons in the Dorsal Raphe Nucleus Are Involved in Reward Processing and Affective Behaviors. Biol Psychiatry 2023; 94:842-851. [PMID: 37285896 PMCID: PMC10850692 DOI: 10.1016/j.biopsych.2023.05.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 05/12/2023] [Accepted: 05/24/2023] [Indexed: 06/09/2023]
Abstract
BACKGROUND Mu opioid receptors (MORs) are key for reward processing, mostly studied in dopaminergic pathways. MORs are also expressed in the dorsal raphe nucleus (DRN), which is central for the modulation of reward and mood, but MOR function in the DRN remains underexplored. Here, we investigated whether MOR-expressing neurons of the DRN (DRN-MOR neurons) participate in reward and emotional responses. METHODS We characterized DRN-MOR neurons anatomically using immunohistochemistry and functionally using fiber photometry in responses to morphine and rewarding/aversive stimuli. We tested the effect of opioid uncaging on the DRN on place conditioning. We examined the effect of DRN-MOR neuron optostimulation on positive reinforcement and mood-related behaviors. We mapped their projections and selected DRN-MOR neurons projecting to the lateral hypothalamus for a similar optogenetic experimentation. RESULTS DRN-MOR neurons form a heterogeneous neuronal population essentially composed of GABAergic (gamma-aminobutyric acidergic) and glutamatergic neurons. Calcium activity of DRN-MOR neurons was inhibited by rewarding stimuli and morphine. Local photo-uncaging of oxymorphone in the DRN produced conditioned place preference. DRN-MOR neuron optostimulation triggered real-time place preference and was self-administered, promoted social preference, and reduced anxiety and passive coping. Finally, specific optostimulation of DRN-MOR neurons projecting to the lateral hypothalamus recapitulated the reinforcing effects of total DRN-MOR neuron stimulation. CONCLUSIONS Our data show that DRN-MOR neurons respond to rewarding stimuli and that their optoactivation has reinforcing effects and promotes positive emotional responses, an activity which is partially mediated by their projections to the lateral hypothalamus. Our study also suggests a complex regulation of DRN activity by MOR opioids, involving mixed inhibition/activation mechanisms that fine-tune DRN function.
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Affiliation(s)
- Lola Welsch
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Esther Colantonio
- INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Mathilde Frison
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada
| | - Desiree A Johnson
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Shannan P McClain
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Victor Mathis
- Centre National de la Recherche Scientifique, Université de Strasbourg, Institut des Neurosciences Cellulaires et Intégratives, UPR 3212, Strasbourg, France
| | - Matthew R Banghart
- Neurobiology Department, School of the Biological Sciences, University of California San Diego, La Jolla, California
| | - Sami Ben Hamida
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM UMR 1247, Université de Picardie Jules Verne, Amiens, France
| | - Emmanuel Darcq
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France
| | - Brigitte L Kieffer
- Douglas Research Center, Department of Psychiatry, McGill University, Montréal, Quebec, Canada; INSERM U1114, Department of Psychiatry, University of Strasbourg, Strasbourg, France.
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