Environmental enrichment modulates the response to chronic stress in zebrafish.

Several studies have shown that manipulations to the housing environment modulate susceptibility to stress in laboratory animals, mainly in rodents. Environmental enrichment (EE) is one such manipulation that promotes neuroprotection and neurogenesis, besides affecting behaviors such as drug self-administration. Zebrafish are a popular and useful animal model for behavioral neuroscience studies; however, studies evaluating the impact of housing conditions in this species are scarce. In this study, we verified the effects of EE on behavioral (novel tank test) and biochemical [cortisol and reactive oxygen species (ROS)] parameters in zebrafish submitted to unpredictable chronic stress (UCS). Consistent with our previous findings, UCS increased anxiety-like behavior, cortisol and ROS levels in zebrafish. EE for 21 or 28 days attenuated the effects induced by UCS on behavior and cortisol, and prevented the effects on ROS levels. Our findings reinforce the idea that EE exerts neuromodulatory effects across species, reducing vulnerability to stress and its biochemical impact. Also, these results indicate that zebrafish is a suitable model animal to study the behavioral effects and neurobiological mechanisms related to EE.