No abstract

In this study, we evaluated the effects of tebuconazole on morphology and exploratory larvae behavior and adult locomotion. Furthermore, we analyzed the effects of this fungicide on AChE activity and gene expression in zebrafish larvae and in the adult zebrafish brain. Tebuconazole (4 mg/L) increased the ocular distance in larvae and reduced the distance travelled, absolute turn angle, line crossing and time outside area in exposed larvae. Moreover, adult zebrafish that were exposed to this fungicide (4 and 6 mg/L) showed a decrease in distance travelled and mean speed when compared to the control group. However, tebuconazole did not alter the number of line crossings or time spent in the upper zone. Tebuconazole inhibited AChE activity at concentrations of 4 mg/L for larvae and 4 and 6 mg/L in the adult zebrafish brain. However, this fungicide did not alter AChE gene expression in the adult zebrafish brain but increased AChE mRNA transcript levels in larvae. These findings demonstrated that tebuconazole could modulate the cholinergic system by altering AChE activity and that this change may be associated with the reduced locomotion of these animals.

No abstract

Methionine (Met) has important functions for homeostasis of various species, including zebrafish. However, the increased levels of this amino acid in plasma, a condition known as hypermethioninemia, can lead to cell alterations. Met is crucial for the methylation process and its excesses interfere with the cell cycle, an effect that persists even after the removal of this amino acid. Some conditions may lead to a transient increase of this amino acid with unexplored persistent effects of Met exposure. In the present study, we investigated the behavioral and neurochemical effects after the withdrawal of Met exposure. Zebrafish were divided into two groups: control and Met-treated group (3 mM) for 7 days and after maintained for 8 days in tanks containing only water. In the eighth day post-exposure, we evaluated locomotion, anxiety, aggression, social interaction, and memory, as well as oxidative stress parameters, amino acid, and neurotransmitter levels in the zebrafish brain. Our results showed that 8 days after Met exposure, the treated group showed decreased locomotion and aggressive responses, as well as impaired aversive memory. The Met withdrawal did not change thiobarbituric acid reactive substances, reactive oxygen species, and nitrite levels; however, we observed a decrease in antioxidant enzymes superoxide dismutase, catalase, and total thiols. Epinephrine and cysteine levels were decreased after the Met withdrawal whereas carnitine and creatine levels were elevated. Our findings indicate that a transient increase in Met causes persistent neurotoxicity, observed by behavioral and cognitive changes after Met withdrawal and that the mechanisms underlying these effects are related to changes in antioxidant system, amino acid, and neurotransmitter levels.

No abstract