First evidence that waterborne methylphenidate alters endocrine and behavioral stress responses in zebrafish.

Several studies have reported the presence of methylphenidate (MPH) in effluents; however, its impacts on aquatic life are not yet well understood. Here, we investigated the effects of acute exposure on endocrine and behavioral stress responses to environmentally relevant concentrations of MPH in zebrafish. We show that MPH blunts the response of cortisol to stress in zebrafish. On the other hand, MPH stresses fish per se. Additionally, MPH seems to modulate anxiety-like behaviors. We conclude that the presence of MPH in aquatic environments can alter neuroendocrine and behavior responses, which might considerably impact fish survival and welfare.