Serotonin (also known as 5-hydroxytryptamine (5-HT)) is a neurotransmitter that has an essential role in the regulation of emotion. However, the precise circuits have not yet been defined through which aversive states are orchestrated by 5-HT. Here we show that 5-HT from the dorsal raphe nucleus (5-HTDRN) enhances fear and anxiety and activates a subpopulation of corticotropin-releasing factor (CRF) neurons in the bed nucleus of the stria terminalis (CRFBNST) in mice. Specifically, 5-HTDRN projections to the BNST, via actions at 5-HT2C receptors (5-HT2CRs), engage a CRFBNST inhibitory microcircuit that silences anxiolytic BNST outputs to the ventral tegmental area and lateral hypothalamus. Furthermore, we demonstrate that this CRFBNST inhibitory circuit underlies aversive behaviour following acute exposure to selective serotonin reuptake inhibitors (SSRIs). This early aversive effect is mediated via the corticotrophin-releasing factor type 1 receptor (CRF1R, also known as CRHR1), given that CRF1R antagonism is sufficient to prevent acute SSRI-induced enhancements in aversive learning. These results reveal an essential 5-HTDRN→CRFBNST circuit governing fear and anxiety, and provide a potential mechanistic explanation for the clinical observation of early adverse events to SSRI treatment in some patients with anxiety disorders1,2.

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We acknowledge B. Roth for providing DREADD viral constructs and SertCre mice, and B. Lowell for providing CrfCre mice. We also thank A. Lopez, D. Perron, and A. Kendra for technical assistance with stereotaxic surgeries on mice, B. Geenen for technical assistance with immunohistochemistry and E. Dankoski for technical assistance with the FSCV. This work was supported by NIH grants AA019454, AA011605 (T.L.K.), the Wellcome Trust (098012) and the Biotechnology and Biological Sciences Research Council grant (BB/K001418/1) (L.K.H.) and by NIH grant K01AA023555 and the Alcohol Beverage Medical Research Fund (Z.A.M.). C.A.M. was supported by a postdoctoral NIAAA F32 fellowship (AA021319-02). C.M.M. is supported by a predoctoral NIAAA F31 fellowship (F31AA023440).

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Author notes

    • Catherine A. Marcinkiewcz
    •  & Christopher M. Mazzone

    These authors contributed equally to this work.


  1. Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA

    • Catherine A. Marcinkiewcz
    • , Christopher M. Mazzone
    • , J. Andrew Hardaway
    • , Jeffrey F. DiBerto
    • , Cayce E. Dorrier
    • , Gregory J. Tipton
    • , Todd E. Thiele
    • , Zoe A. McElligott
    •  & Thomas L. Kash
  2. Curriculum in Neurobiology, School of Medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina 27599, USA

    • Christopher M. Mazzone
    •  & Thomas L. Kash
  3. Rowett Institute of Nutrition and Health, University of Aberdeen, Aberdeen AB25 2ZD, UK

    • Giuseppe D’Agostino
    • , Claudia Cristiano
    •  & Lora K. Heisler
  4. National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852-9411, USA

    • Lindsay R. Halladay
    •  & Andrew Holmes
  5. Department of Psychology & Neuroscience, College of Arts and Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA

    • Montserrat Navarro
    • , Nathan Burnham
    • , Todd E. Thiele
    •  & Thomas L. Kash
  6. Department of Bioengineering, Stanford University, Stanford, California 94305, USA

    • Charu Ramakrishnan
    •  & Karl Deisseroth
  7. Hayward Genetics Center, Tulane University, New Orleans, Louisiana 70112, USA

    • Tamas Kozicz
  8. Department of Anatomy, Radboud University Nijmegen Medical Center, 6500HB Nijmegen, The Netherlands

    • Tamas Kozicz
  9. Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA

    • Zoe A. McElligott
  10. Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA

    • Thomas L. Kash


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C.A.M., C.M.M., G.D., Z.A.M., L.K.H. and T.L.K. designed the experiments. A.H. and J.F.D. performed triple label fos/tryptophan hydroxylase/Fluor-Gold staining and image analysis. L.R.H. performed electrode placement surgeries and in vivo recordings during fear acquisition and recall. C.A.M. performed stereotaxic surgeries for evoked 5-HT electrophysiology and optogenetic behavioural experiments. Z.A.M. performed slice FSCV experiments and C.A.M. performed evoked 5-HT electrophysiology experiments. C.A.M. performed stereotaxic surgeries, behavioural and data analysis for 5-HTDRN→BNST optogenetic experiments. C.A.M. performed all slice electrophysiology experiments and C.M.M. and C.A.M. performed stereotaxic surgeries for these experiments (retrograde tracers, ChR2 infusions, and hM3D and hM4D infusions), C.M.M. performed stereotaxic surgeries for chemogenetic manipulations in CRFBNST neurons that were used in fluoxetine fear conditioning experiments and C.A.M. performed behavioural and data analysis. C.E.D. performed surgeries for electrophysiological recordings and data analysis for fear conditioning experiments. M.N. and J.F.D. performed surgeries for chemogenetic manipulations in CRFBNST neurons that were used in fluoxetine anxiety (EZM) assays and N.B. and C.A.M. performed behavioural and data analysis. C.M.M. and J.F.D. performed stereotaxic surgeries for HSVCre::hM3DBNST behavioural manipulations and C.A.M. performed behavioural and data analysis. C.M.M. also performed imaging and analysis for optogenetic experiments, chemogenetic, and Intrsect experiments. C.R. and K.D. designed Intrsect viral constructs. G.D. and C.C. performed surgeries, behavioural and data analysis for Htr2cCre::hM3DBNST experiments. C.A.M., C.M.M. and T.L.K. wrote the manuscript with input from Z.A.M., L.R.H., J.F.D., J.A.H., G.D., T.E.T., A.H., L.K.H. and T.K.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Thomas L. Kash.

Reviewer Information Nature thanks A. Sahay and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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