The influence of exercise on anxiety-like behavior in zebrafish (Danio rerio)

In non-human mammals, exercise has been shown to decrease anxiety-like behavior. Conversely, a number of studies have reported no effect or even an increase in anxiety-like behavior after exercise, however, inconsistent training regimes and behavioral paradigms across studies may be confounding the results. Zebrafish (Danio rerio) are a well-established animal model in neurobehavioral research, and have the potential to shed new insight into the effects of exercise on anxiety-like behavior where previous research has been limited, due to the ability to precisely control intensity and duration of exercise, and the validation of tests for measuring different aspects of anxiety-like behaviors. In the current study, fish were split between two treatment groups; Exercised and Control. Fish in the exercised condition were aerobically challenged (max water velocity: 0.5 m/s) using a swim tunnel one hour a day, five days a week, for six weeks. Control fish spent an equal amount of time in the swim tunnel but were not aerobically challenged (max water velocity: 0.05 m/s). After six weeks, all fish were tested individually in two standard complimentary anxiety tests for zebrafish: the novel tank test and the light-dark test. Exercised fish exhibited reduced anxiety-like behaviors in the novel tank test; they spent more time in the top and were quicker to enter the top of a novel tank compared to Control fish. In addition, Exercised fish spent more time in the light compartment of the light-dark test compared to Control fish. Our results demonstrate the beneficial effect of exercise on anxiety-like behavior in zebrafish.