Modeling of stress and anxiety in adult zebrafish (Danio rerio) is increasingly utilized in neuroscience research and central nervous system (CNS) drug discovery. Representing the most commonly used zebrafish anxiety models, the novel tank test (NTT) focuses on zebrafish diving in response to potentially threatening stimuli, whereas the light-dark test (LDT) is based on fish scototaxis (innate preference for dark vs. bright areas). Here, we systematically evaluate the utility of these two tests, combining meta-analyses of published literature with comparative in vivo behavioral and whole-body endocrine (cortisol) testing. Overall, the NTT and LDT behaviors demonstrate a generally good cross-test correlation in vivo, whereas meta-analyses of published literature show that both tests have similar sensitivity to zebrafish anxiety-like states. Finally, NTT evokes higher levels of cortisol, likely representing a more stressful procedure than LDT. Collectively, our study reappraises NTT and LDT for studying anxiety-like states in zebrafish, and emphasizes their developing utility for neurobehavioral research. These findings can help optimize drug screening procedures by choosing more appropriate models for testing anxiolytic or anxiogenic drugs.

Introduction: Depression, anxiety and other affective disorders are globally widespread and severely debilitating human brain diseases. Despite their high prevalence and mental health impact, affective pathogenesis is poorly understood, and often remains recurrent and resistant to treatment. The lack of efficient antidepressants and presently limited conceptual innovation necessitate novel approaches and new drug targets in the field of antidepressant therapy. Areas covered: Herein, the authors discuss the emerging role of neuro-immune interactions in affective pathogenesis, which can become useful targets for CNS drug discovery, including modulating neuroinflammatory pathways to alleviate affective pathogenesis. Expert opinion: Mounting evidence implicates microglia, polyunsaturated fatty acids (PUFAs), glucocorticoids and gut microbiota in both inflammation and depression. It is suggested that novel antidepressants can be developed based on targeting microglia-, PUFAs-, glucocorticoid- and gut microbiota-mediated cellular pathways. In addition, the authors call for a wider application of novel model organisms, such as zebrafish, in studying shared, evolutionarily conserved (and therefore, core) neuro-immune mechanisms of depression.