Influência da melatonina sobre os parâmetros de locomoção e estresse em Zebrafish (Danio rerio)

Abstract

This work had the objective of investigating the influence of melatonin over locomotion parameters and stress of Zebrafish (Danio rerio). We divided 400 Zebrafish into two groups (animals subjected and not subjected to stress), on which we tested different doses of melatonin (0M = 0; 1M = 10 nM; 2M = 0.001 mM; 3M = 0.1 mM). In Experiment 1, we analyzed biochemical variables: plasma glucose (ventricular perforation), body lactate (maceration/commercial kit) and body cortisol (maceration/commercial kit). In Experiment 2, we analyzed behavioral variables: locomotive activity (quadrant change count) and anxiety (time of permanence at the bottom of the aquarium). The results found for plasma glucose (mg/dL) and body lactate (mg/g) were insignificant (p>0.05), suggesting that, despite being stress indicating parameters, perhaps they are not applicable to Zebrafish. Regarding the cortisol (ng/g), there was significant difference between melatonin doses (p<0.01), which presented quadratic effect. The results found for quadrant change were significant (p<0.05), in which the highest dose of melatonin (3M = 0.1 mM) was capable of containing the increase in locomotive activity of the stressed animals. Most animals remained at the bottom of the aquarium and, the highest dose of melatonin (3M = 0.1 mM) was capable of, significantly (p<0.05), containing the increase of anxiety. Therefore, the results obtained allowed us to conclude that only the melatonin dose of 0.1 mM was determining in containing the increase in the levels of body cortisol, locomotive activity and anxiety in Zebrafish ( Danio rerio) subjected to stress.