Serotonin is a neurotransmitter involved in many psychiatric diseases. In humans, a lack of 5-HT2B receptors is associated with serotonin-dependent phenotypes, including impulsivity and suicidality. A lack of 5-HT2B receptors in mice eliminates the effects of molecules that directly target serotonergic neurons including amphetamine derivative serotonin releasers, and selective serotonin reuptake inhibitor antidepressants. In this work, we tested the hypothesis that 5-HT2B receptors directly and positively regulate raphe serotonin neuron activity. By ex vivo electrophysiological recordings, we report that stimulation by the 5-HT2B receptor agonist, BW723C86, increased the firing frequency of serotonin Pet1-positive neurons. Viral overexpression of 5-HT2B receptors in these neurons increased their excitability. Furthermore, in vivo 5-HT2B-receptor stimulation by BW723C86 counteracted 5-HT1A autoreceptor-dependent reduction in firing rate and hypothermic response in wild-type mice. By a conditional genetic ablation that eliminates 5-HT2B receptor expression specifically and exclusively from Pet1-positive serotonin neurons (Htr2b5-HTKO mice), we demonstrated that behavioral and sensitizing effects of MDMA (3,4-methylenedioxy-methamphetamine), as well as acute behavioral and chronic neurogenic effects of the antidepressant fluoxetine, require 5-HT2B receptor expression in serotonergic neurons. In Htr2b5-HTKO mice, dorsal raphe serotonin neurons displayed a lower firing frequency compared to control Htr2blox/lox mice as assessed by in vivo extracellular recordings and a stronger hypothermic effect of 5-HT1A-autoreceptor stimulation was observed. The increase in head-twitch response to DOI (2,5-dimethoxy-4-iodoamphetamine) further confirmed the lower serotonergic tone resulting from the absence of 5-HT2B receptors in serotonin neurons. Together, these observations indicate that the 5-HT2B receptor acts as a direct positive modulator of serotonin Pet1-positive neurons in an opposite way as the known 5-HT1A-negative autoreceptor.

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We thank the Mouse Clinical Institute (Strasbourg) for Htr2b-floxed mice production, Evan Deneris for providing Pet1-Cre BAC transgenic mice, Mythili Savariradjane and the Imaging facility of the IFM, and Natacha Roblot and the IFM animal facility.


This work has been supported by funds from the Centre National de la Recherche Scientifique, the Institut National de la Santé et de la Recherche Médicale, the Université Pierre et Marie Curie, and by grants from the Fondation pour la Recherche Médicale “Equipe FRM DEQ2014039529”, the French Ministry of Research (Agence Nationale pour la Recherche ANR-12-BSV1-0015 and ANR-17-CE16-0008 and the Investissements d’Avenir programme ANR-11-IDEX-0004-02). LM’s team is part of the École des Neurosciences de Paris Ile-de-France network and of the Bio-Psy Labex and as such this work was supported by French state funds managed by the ANR within the Investissements d’Avenir programme under reference ANR-11-IDEX-0004-02.

Author contributions

AB, EQ, SLD, SPF, SD, SMB, PMP, IM, AM, and AT conducted the experiments; AR conducted and designed the experiments; BPG conducted, designed the experiments, and wrote the paper; MM supervised, wrote the paper, and provided funding; LM supervised, wrote the paper, and provided funding.

Author information

Author notes

  1. Arnauld Belmer and Emily Quentin contributed equally to this work.


  1. INSERM UMR-S 839, 75005, Paris, France

    • Arnauld Belmer
    • , Emily Quentin
    • , Silvina L. Diaz
    • , Sebastian P. Fernandez
    • , Stéphane Doly
    • , Sophie M. Banas
    • , Pothitos M. Pitychoutis
    • , Imane Moutkine
    • , Aude Muzerelle
    • , Anna Tchenio
    • , Anne Roumier
    • , Manuel Mameli
    •  & Luc Maroteaux
  2. Sorbonne Universités, UPMC Univ Paris 6, 75005, Paris, France

    • Arnauld Belmer
    • , Emily Quentin
    • , Silvina L. Diaz
    • , Sebastian P. Fernandez
    • , Stéphane Doly
    • , Sophie M. Banas
    • , Pothitos M. Pitychoutis
    • , Imane Moutkine
    • , Aude Muzerelle
    • , Anna Tchenio
    • , Anne Roumier
    • , Manuel Mameli
    •  & Luc Maroteaux
  3. Institut du Fer à Moulin, 75005, Paris, France

    • Arnauld Belmer
    • , Emily Quentin
    • , Silvina L. Diaz
    • , Sebastian P. Fernandez
    • , Stéphane Doly
    • , Sophie M. Banas
    • , Pothitos M. Pitychoutis
    • , Imane Moutkine
    • , Aude Muzerelle
    • , Anna Tchenio
    • , Anne Roumier
    • , Manuel Mameli
    •  & Luc Maroteaux
  4. Translational Research Institute, Queensland University of Technology, Brisbane, QLD, 4059, Australia

    • Arnauld Belmer
  5. Instituto de Biología Celular y Neurociencia, Fac. de Cs. Exactas, Químicas y Naturales, Universidad de Morón, UBA-CONICET – Paraguay 2155, 3° piso, C1121ABG, Buenos Aires, Argentina

    • Silvina L. Diaz
  6. Research Center on Animal Cognition, Center for Integrative Biology, 31062, Toulouse, France

    • Bruno P. Guiard
  7. Université Paul Sabatier, 31062, Toulouse, France

    • Bruno P. Guiard
  8. UMR5169 CNRS, 31062, Toulouse, France

    • Bruno P. Guiard
  9. IPMC – CNRS UMR7275 660 Route des Lucioles Sophia-Antipolis, 06560, Valbonne, France

    • Sebastian P. Fernandez
  10. Université Clermont Auvergne, INSERM, NEURO-DOL, 63000, Clermont-Ferrand, France

    • Stéphane Doly
  11. Department of Biology and Center for Tissue Regeneration and Engineering at Dayton (TREND), University of Dayton, Dayton, OH, USA

    • Pothitos M. Pitychoutis
  12. Dept. Fundamental Neurosciences (DNF) The University of Lausanne, Lausanne, Switzerland

    • Anna Tchenio
    •  & Manuel Mameli


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Conflict of interest

AR has been supported by grants from the Université Pierre et Marie Curie (Emergence-UPMC program) and the Bio-Psy Labex. SD has been supported by a fellowship of the Lefoulon-DeLalande foundation, SLD from the Region Ile-de France DIM STEM and from the ANPCyT (PICT 2013-3225), CONICET (PIP-11220130100157CO), and University of Moron (PID 2015), and EQ by a PhD fellowship from the Region Ile-de France DIM Cerveau et Pensée. The other authors declare that they have no conflict of interest.

Corresponding author

Correspondence to Luc Maroteaux.

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