The role of taurine on anxiety-like behaviors in zebrafish: A comparative study using the novel tank and the light-dark tasks.

Taurine (TAU) is an amino sulfonic acid with several functions in central nervous system. Mounting evidence suggests that it acts in osmoregulation, neuromodulation and also as an inhibitory neurotransmitter. However, the effects of TAU on behavioral functions, especially on anxiety-related parameters, are limited. The adult zebrafish is a suitable model organism to examine anxiety-like behaviors since it presents neurotransmitter systems and behavioral functions evolutionary conserved. Anxiety in zebrafish can be measured by different tasks, analyzing the habituation to novelty, as well as the response to brightly lit environments. The aim of this study was to investigate whether acute TAU treatment alters anxiety-like behavior in zebrafish using the novel tank and the light-dark tests. Fish were individually treated with TAU (42, 150, and 400mg/L) for 1h and the behaviors were further analyzed for 6min in the novel tank or in the light-dark test. Control fish were handled in a similar manner, but kept only in home tank water. Although TAU did not alter locomotor and vertical activities, all concentrations significantly increased shuttling and time spent in lit compartment. Moreover, TAU 150 group showed a significant decrease in the number of risk assessment episodes. Overall, these data suggest that TAU exerts an anxiolytic-like effect in zebrafish and the comparative analysis of behavior using different tasks is an interesting strategy for neuropsychiatric studies related to anxiety in this species.

Strain- and context-dependent behavioural responses of acute alarm substance exposure in zebrafish.

We investigate the behavioural responses of wild type (WT) and leopard (leo) zebrafish elicited by alarm substances of conspecifics at three contexts: during the exposure period (Experiment 1); after exposure, in habituation to novelty (Experiment 2); or after exposure, in the light-dark preference test (Experiment 3), and analyse their influence on pigment response. During the exposure, leo showed decreased vertical drifts, increased number and duration of erratic movements, while WT had increased erratic movements and latency to enter the top. In the novel tank, we observed that angular velocity decreased in WT exposed to alarm substance, which also presented increased fear responses. Contrastingly, leo increased the number of entries and time in top, indicating differences in habituation profile. Alarm substance increased the number of erratic movements in the light-dark test, but elicited different responses between strains in scototaxis, latency to enter the dark compartment and risk assessment episodes. Moreover, the body colour of zebrafish did not change after alarm substance exposure. Principal component analyses suggest that burst swimming, anxiety-like behaviours, and locomotion/exploration were the components that most accounted for total variances of Experiments 1, 2, and 3, respectively. We conclude that chemical cue from conspecifics triggers strain- and context-dependent responses.

Modulatory action of taurine on ethanol-induced aggressive behavior in zebrafish.

Alcohol is a potent agent for eliciting aggression in vertebrates. Taurine (TAU) is an amino sulfonic acid with pleiotropic actions on brain function. It is one of the most abundant molecules present in energy drinks frequently used as mixers for alcoholic beverages. However, the combined effects of TAU and ethanol (EtOH) on behavioral parameters such as aggression are poorly understood. Considering that zebrafish is a suitable vertebrate to assess agonistic behaviors using noninvasive protocols, we investigate whether TAU modulates EtOH-induced aggression in zebrafish using the mirror-induced aggression (MIA) test. Since body color can be altered by pharmacological agents and may be indicative of emotional state, we also evaluated the actions of EtOH and TAU on pigment response. Fish were acutely exposed to TAU (42, 150, and 400mg/L), EtOH (0.25%), or cotreated with both molecules for 1h and then placed in the test apparatus for 6min. EtOH, TAU 42, TAU 400, TAU 42/EtOH and TAU 400/EtOH showed increased aggression, while 150mg/L TAU only increased the latency to attack the mirror. This same concentration also prevented EtOH-induced aggression, suggesting that it antagonizes the effects of acute alcohol exposure. Representative ethograms revealed the existence of different aggressive patterns and our results were confirmed by an index used to estimate aggression in the MIA test. TAU did not alter pigment intensity, while EtOH and all cotreated groups presented a substantial increase in body color. Overall, these data show a biphasic effect of TAU on EtOH-induced aggression of zebrafish, which is not necessarily associated with changes in body color.