Behavioral and neurotoxic effects of arsenic exposure in zebrafish (Danio rerio, Teleostei: Cyprinidae).

This study investigated the passive avoidance conditioning in zebrafish (Danio rerio). An instrument was developed for measuring escape responses triggered by a conditioned stimulus. This system allowed quantification of latency of crossing from a light to a dark zone. Zebrafish were trained to swim from an illuminated to a dark compartment, where they received a body shock (training session). The proposed methodology was efficient for evaluation of working, short, and long-term memory formation of an aquatic animal model. The possibility of employing memory measurements in toxicity tests, in order to obtain an ecologically meaningful biomarker response, was also analyzed. In this experiment, immediately after the training session, fish were exposed to three arsenic (As(V)) concentrations. After the test session, the brain was removed for biochemical analyses. A control group was kept in tap water. After exposure, animals were submitted to a one-trial inhibitory avoidance test for measurement of long-term memory (LTM). Results from behavioral and biochemical analyses showed that the three As(V) concentrations impaired LTM (p<0.05) and increased protein oxidation, which suggests an amnesic and pro-oxidant effect of As(V). Evaluation of behavior parameters in aquatic models is an important complement in studies concerning the environmental impact of chemical substances.

Modulation of antioxidant and detoxification responses mediated by lipoic acid in the fish Corydoras paleatus (Callychthyidae).

Lipoic acid (LA) has been reported as a potential therapeutic agent due its antioxidants proprieties. It was considered its effect in different organs (gills, brain, muscle and liver) of the fish Corydoras paleatus (Callychthyidae). LA (70 mg/kg of body mass) was added to a commercial fish diet, organisms being fed daily (1% body weight). Sixty animals (mean mass: 2.37+/-0.09 g) were placed randomly in aquariums and received (+LA) or not (-LA) lipoic acid enriched diet during four weeks. After, fish were killed and the brain, muscle, gills and liver were dissected. LA treatment reduced significantly (p<0.05) reactive oxygen species concentration in brain and increased (p<0.05) glutamate-cysteine ligase activity in brain and liver of the same experimental group. LA fed organisms showed higher (p<0.05) brain glutathione-S-transferase activity, indicating that LA improves the detoxification and antioxidant capacity face components that waste glutathione in phase II reactions. A conspicuous reduction of protein oxidation was observed in muscle and liver of +LA organisms, indicating that the treatment was also effective in reducing oxidative stress parameters.