Preclinical Drug Screening for Depression
Modern drug discovery for depression relies on cognitive-affective biomarkers that mirror human depression, moving beyond old “behavioural despair” assays (forced swim test) which have poor face validity. The standard experimental architecture uses translationally validated nonverbal-cognitive-tasks.
Disease Model Induction
Before drug screening, a valid depression-like state must be induced in rodent cohorts:
| Protocol | Duration | Key Feature |
|---|---|---|
| Chronic Unpredictable Mild Stress (CUMS) | 4-6 weeks | Shifting environmental stressors (bedding deprivation, cage tilting, altered light cycles) |
| Social Defeat Stress (SDS) | Variable | Social avoidance and anhedonia via aggressive dominant mouse |
| Pharmacological (Tetrabenazine) | Acute | Monoamine depletion |
| Pharmacological (LPS) | Acute | Neuroinflammation-induced cognitive deficits |
Primary Screening Tasks
Task A: affective-bias-test — bowl-digging or touchscreen assay. Measures how a drug modifies emotional memory encoding/retrieval. Depressed controls avoid negatively-associated substrate; effective antidepressants (ketamine, psilocybin) attenuate negative memory bias.
Task B: cognitive-judgement-bias — operant box “pessimism” task. Differentiates rapid-acting (instant shift to optimism) from conventional (2-3 week latency) antidepressant mechanisms.
Treatment Cohort Configuration
Healthy → Vehicle Control + Drug Control
Depressed (CUMS/SDS) → +Vehicle, +Reference Drug, +Candidate Drug
Key Metrics
- Choice Bias Ratio — Positive Choice Responses / Total Responses
- Omission Rates — Distinguish cognitive recovery from sedation
- Locomotor Activity Control — Open field test to rule out psychostimulant confounds
- Sustained vs. Acute Clearance — Test at 1-hour (acute) and 24-hour (sustained) post-dose to identify long-lasting neuroplastic adjustments
Related Pages
nonverbal-cognitive-tasks | affective-bias-test | cognitive-judgement-bias | delayed-match-to-sample | macaque-target-validation