Diazepam e fluoxetina inibem a resposta de estresse em zebrafish (Danio rerio)

Abstract

The presence of pharmaceuticals in the aquatic environment has long been reported for some years in various studies. However, the impact of drugs on organisms present in aquatic ecosystems is still poorly known. Thus, we investigated the effects of acute exposure to diazepam or fluoxetine on the response to acute stress in zebrafish (Danio rerio). Fish were exposed to drugs for 15 minutes and, after this period, the group designated time 0 was collected; the other groups were subjected to a stimulus of stress, which consisted in persecution of fish with a net for two minutes, and after that, were collected at the times of 15, 60 and 240 minutes. Three concentrations of diazepam 0.88 μg/L (environmental concentration) were used; 16 μg/L; and 160 μg/L, concentrations that cause behavioral effects in zebrafish. Regarding fluoxetine at concentrations of 1 μg/L, 25 μg/L and 50 μg/L (25 to 50 times the concentration of the environment, respectively) were used. Our results show that diazepam and fluoxetine inhibit the axis of stress in the zebrafish. The intermediate concentration of diazepam is able to suppress the stress response, as measured by levels of cortisol whereas the fluoxetine is able to inhibit the stress response at concentrations similar to those found in the environment. Fish with an impaired stress response loses the ability to maintain homeostasis against stress factors, since it reduces the ability to promote ionic, metabolic and behavioral adjustments necessary for such response. Thus, these data suggest that the presence of psychoactive drugs in aquatic ecosystems may cause neuroendocrine dysfunction in fish.