Cited by 233Neurotransmitter Receptor Influence on BehaviorTreatment of Major DepressionNeuroscience and Neuropharmacology Research

The DOI matches its Crossref record; 210 of the 210 references it cites were found in a registry or an index; 2 of the 217 sources its claims cite were checked for support.

The molecular and cellular mechanisms of depression: a focus on reward circuitry

Open access
Fox, Megan E., Lobo, Mary Kay·2019·Molecular Psychiatry

Abstract

Depression is a complex disorder that takes an enormous toll on individual health. As affected individuals display a wide variation in their clinical symptoms, the precise neural mechanisms underlying the development of depression remain elusive. Although it is impossible to phenocopy every symptom of human depression in rodents, the preclinical field has had great success in modeling some of the core affective and neurovegetative depressive symptoms, including social withdrawal, anhedonia, and weight loss. Adaptations in select cell populations may underlie these individual depressive symptoms and new tools have expanded our ability to monitor and manipulate specific cell types. This review outlines some of the most recent preclinical discoveries on the molecular and neurophysiological mechanisms in reward circuitry that underlie the expression of behavioral constructs relevant to depressive symptoms.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This review synthesizes preclinical evidence on molecular and cellular adaptations in ventral tegmental area (VTA) and nucleus accumbens (NAc) reward circuitry that underlie depression-like behaviors, especially anhedonia and social withdrawal. It emphasizes cell-type-specific and sometimes bidirectional changes across stress models and calls for more work on non-neuronal cells, sex differences, and treatment-resistant depression.

Key findings

  • Stress produces divergent VTA dopamine neuron activity: chronic social defeat stress (CSDS) increases VTA dopamine neuron firing, with increased Ih currents in NAc-projecting but not mPFC-projecting neurons; inhibiting NAc-projecting VTA dopamine neurons induces resilience, whereas inhibiting mPFC projections promotes susceptibility. Chronic mild or cold stress instead reduces VTA population activity, an effect more pronounced in females.
  • In NAc, chronic stress causes opposing medium spiny neuron (MSN) subtype changes: excitatory input is weakened onto D1-MSNs and strengthened onto D2-MSNs; optogenetic D1-MSN stimulation reverses social and sucrose preference deficits, while D2-MSN stimulation enhances stress susceptibility. D1-MSN dendritic complexity is reduced in CSDS-susceptible mice, and D1-MSN RhoA/Egr3 signaling promotes susceptibility.
  • Molecular adaptations include BDNF-TrkB, AKT, ERK2, Cdk5, Otx2, CREB/ΔFosB, β-catenin/Dicer1, Dnmt3a, Tet1, H3.3, and SIRT1, with cell-type-specific examples such as decreased Slc6a15 in D2-MSNs and decreased Nlgn2 in D1-MSNs of susceptible mice.
  • Non-neuronal and neuroimmune mechanisms are implicated: at least 40% of cells in rodent and human brain are non-neuronal; chronic stress increases IL-6, IL-1β, and CXCL1, recruits monocytes/macrophages, and alters microglia, while anti-inflammatory treatments reduce depressive symptoms in humans. Approximately 95% of NAc neurons are MSNs, but cholinergic interneurons and glia also contribute.

Methods

  • Design: narrative review of preclinical rodent models for depression-like behavior—chronic unpredictable stress (CUS; 8–12 weeks), learned helplessness, and CSDS (10 days; approximately 70% stress-susceptible, ~30% stress-resilient)—integrated with human functional imaging and postmortem MDD findings.
  • Data or sample: no new experimental data; synthesizes cited rodent studies using male, female, and adolescent mice/rats, plus human postmortem MDD tissue and imaging studies.
  • Main analysis: qualitative synthesis of electrophysiological, optogenetic, viral, transcriptomic, epigenetic, structural, and behavioral findings, with proposed remaining questions rather than a systematic or quantitative meta-analysis.

Limitations

  • The paper states that many questions remain, including whether bidirectional VTA activity changes reflect stress paradigm, symptom type, or distinct cell populations; most NAc D1/D2-MSN work was done solely in male rodents; validation relies heavily on postmortem MDD tissue often from suicide completers; and new antidepressants have not been approved despite rodent progress.
  • The paper states that preclinical models cannot phenocopy all human depression symptoms, that forced-swim/tail-suspension interpretations have been questioned, and that treatment-resistant populations are understudied.
  • Evident from the text: as a narrative review, it lacks a systematic search or meta-analysis, and conclusions depend on cited studies with heterogeneous stress paradigms, housing conditions, sex inclusion, and cell-type specificity.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41380-019-0415-3

Cites

210 of 210 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

159 Not checked yet · 7 Own interpretation · 1 Supported · 1 Supported so far

Verify all 215 references — free account

Show all 115 claims

  • It may state two separate claims as one. 49
  • Probably not a substantial claim. 4
53 of 53
  • The paper relies on this without support.

    Altered reward circuit function underlies the loss of pleasure and amotivational syndrome experienced by most major depressive disorder patients.

    “Altered reward circuit function is theorized to underlie the loss of pleasure and amotivational syndrome experienced by most MDD patients”
  • The paper relies on this without support.

    Preclinical rodent models are useful for identifying cell-type-specific mechanisms that are otherwise inaccessible in human studies.

    “Preclinical rodent models for studying depression have been useful for identifying the cell-type-specific mechanisms that are otherwise inaccessible in human studies.”
  • The paper relies on this without support.

    Rats and mice do not likely experience the complex cognitive aspects of clinical depression.

    “Although rats and mice do not likely experience the complex cognitive aspects of clinical depression”
  • The paper relies on this without support.

    Rodents, similar to humans, want to work for rewards such as food, sex, and social interaction.

    “rodents, similar to humans, want to work for rewards such as food, sex, and social interaction.”
  • The paper relies on this without support.

    The stressful experiences that precipitate major depressive disorder likely represent a combination of physical and psychosocial stressors.

    “the stressful experiences that precipitate MDD likely represent a combination thereof.”
  • The paper relies on this without support.

    Postmortem MDD brain tissue gene expression changes reflect antemortem MDD pathophysiology.

    “Much of the validation of the molecular changes found in rodents relies on tissue collected from postmortem MDD brains.”
  • The paper relies on this without support.

    Rodent chronic stress models such as CSDS and CUS produce depressive-like states relevant to human MDD.

    “Together, these studies provide insight into how stress exposure alters NAc MSN physiology to elicit depressive behavior.”
7 of 7

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Citations

Cites

1 retracted

Show all 209 references

Cited by

Sorted by citations

Items 201–233 of 233

Metadata

Authors
Fox, M. E., & Lobo, M. K.
Affiliations
University of Maryland, Baltimore (US)
Corresponding author
Lobo, Mary Kay
Venue
Molecular Psychiatry
Published
2019-04-09
Volume
24
Issue
12
Pages
1798-1815
ISSN
  • 1359-4184 (ISSN-L)
  • 1476-5578
OpenAlex
W2937907669
Cited by
232
References
209
Citations by year
2026: 19 · 2025: 41 · 2024: 37 · 2023: 41 · 2022: 40 · 2021: 38 · 2020: 13 · 2019: 2
FWCI
3.13
Type
journal article
Language
en
Open access
Locations
  • Molecular Psychiatry (publishedVersion)
  • PubMed (publishedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • U.S. Department of Health & Human Services | NIH | National Institute of Mental Health (R01MH106500, F32 MH116574)
  • U.S. Department of Health & Human Services | NIH | National Institute on Drug Abuse (R01DA038613, R01DA047843)
Topics
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neurotransmitter Receptor Influence on Behavior
  • Health Sciences › Medicine › Pharmacology (medical) › Treatment of Major Depression
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
Keywords
depression, reward systems, anhedonia, social withdrawal, neurovegetative symptoms, weight loss, neurophysiological mechanisms, rodent models of depression
MeSH terms
Animals, Depression, Major Depressive Disorder, Disease Models, Animal, Humans, Motivation, Reward, Social Behavior, Weight Loss, Anhedonia

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-09, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-09 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review