Assessing adult zebrafish despair-like behaviors in the small vertical cylinder immobility test (VCIT)

Background: Affective disorders represent a major global health burden. Animal models are widely used for modeling brain disorders and neuroactive drug discovery. A novel powerful tool in translational neuroscience research, zebrafish (Danio rerio) provide multiple behavioral assays relevant to anxiety-like and depression-related conditions (including despair-like behavior, a common feature in depression). New method: Here, we introduce a novel behavioral paradigm for assessing zebrafish locomotion and despair-like phenotypes, the small 5-mL glass vertical cylinder immobility test (VCIT). Conceptually similar to rodent and other zebrafish ‘despair’-like models, the VCIT protocol is based on restricting fish locomotion vertically for 5 min in head-first position, to assess their locomotion and despair-like immobility. Results: The test was sensitive to acute and chronic stressors that increased immobility duration (alarm pheromone, net chasing, chronic sleep deprivation and 12-week unpredictable stress), as well as to bidirectional modulation of zebrafish behavior by various acute and chronic neuroactive drugs. The VCIT immobility was reduced by psychostimulants nicotine and arecoline, as well as a conventional antidepressant fluoxetine. In contrast, the immobility in this test was increased by a pro-depressant dopamine-depleting drug reserpine, and remained unaltered by an anxiolytic agent ethanol or anxiogenic drugs caffeine and GBR-12909 (vanoxerine). Comparisons with existing method(s): The VCIT provides an easy-to-perform, minimally invasive, non-traumatic, and procedurally simpler and faster model of assessing zebrafish stress-evoked despair-like phenotypes. Conclusions: The VCIT is sensitive to various stress-related manipulations and bidirectional pharmacological modulation, hence emphasizing the growing relevance and potential of zebrafish in advancing neuropsychiatric research and identifying innovative treatments for neuropsychiatric disorders.