Neurobehavioral Effects of Two Distinct Anti-Inflammatory Drugs in a Two-Week Chronic Stress Model in Zebrafish

Background/Objectives: Chronic stress and neuroinflammation (promoted by micro- and astroglia) represent key factors in affective pathogenesis. Complementing rodent models, zebrafish (Danio rerio) are widely used in experimental modeling of affective disorders. Here, we examined the effects of chronic treatment with two distinct anti-inflammatory drugs, minocycline and nimesulide, on behavior and neuroinflammation-related biomarker genes in the zebrafish chronic unpredictable stress (CUS) model. Methods: Following two-week CUS with or without drug treatment, fish were assessed using the novel tank test for anxiety-like behavior, and the zebrafish tail immobilization (ZTI) test for depression-like behavior. Results: A 14-day treatment with minocycline (50 mg/L) reduced general motor activity and brain expression of both pro-inflammatory (nos2a) and anti-inflammatory (arg1) microglial biomarker genes, as well as upregulated the anti-inflammatory astrocytic marker s100a10. In CUS-exposed fish, this treatment attenuated depression-like ZTI immobility behavior and downregulated both pro-inflammatory (nos2a, cox2) and anti-inflammatory (arg1, ptx) glial biomarkers compared to the stress-only control. In contrast, one-week nimesulide treatment during CUS produced an anxiolytic-like effect and normalized the expression of stress-induced pro-inflammatory glial biomarkers cox2 and il1β. Conclusions: Overall, our findings suggest that the two anti-inflammatory drugs tested modulate behavioral and molecular responses to chronic stress in zebrafish, with minocycline demonstrating broader anti-neuroinflammatory and antidepressant-like effects, and nimesulide exhibiting more specific anxiolytic-like properties in this model.