Divergent neurobehavioral signatures of anxiety and depression: a multilevel comparative analysis in adult zebrafish

Background: Stress-related psychiatric disorders such as anxiety and depression require robust preclinical models for mechanistic exploration. In this study, we utilized adult zebrafish (Danio rerio) to investigate behavioral, molecular, and metabolic differences between anxiety- and depression-like states. Methods: Anxiety was modeled using acute predator exposure, whereas depression was induced via a 21-day chronic unpredictable stress (CUS) protocol. Evaluations included behavioral assays, histopathology, immunohistochemistry, untargeted metabolomic profiling, and gene expression analyses. Results: Behavioral assays revealed divergent phenotypes: the anxiety group displayed erratic movement and reduced exploration, whereas the depression-like group exhibited reduced locomotor activity, impaired social behavior, cognitive deficits, and increased immobility in the tail test. Histopathological analysis showed more severe neuronal degeneration in depression. Immunohistochemical staining indicated higher expression of stress markers (BDNF, BMAL1, 5HT4) in both groups, with stronger accumulation in depression. Metabolomics showed widespread upregulation of neurotransmitter-related metabolites in depression, while the anxiety group exhibited selective changes and essential fatty acid depletion. Gene expression revealed broader upregulation of neuropeptides, inflammatory cytokines, and monoamine-related genes in depression. Conclusion: Our findings highlight the ability of zebrafish to model distinct stress-induced affective disorders and underscore how stress duration shapes neurobehavioral and molecular outcomes, supporting their translational utility in psychiatric research.