Natural environment imposes many challenges to animals, which have to use cognitive abilities to cope with and exploit it to enhance their fitness. Since zebrafish is a well-established model for cognitive studies and high-throughput screening for drugs and diseases that affect cognition, we tested their ability for ambient color preference and 3D objects discrimination to establish a protocol for memory evaluation. For the color preference test, zebrafish were observed in a multiple-chamber tank with different environmental color options. Zebrafish showed preference for blue and green, and avoided yellow and red. For the 3D objects discrimination, zebrafish were allowed to explore two equal objects and then observed in a one-trial test in which a new color, size, or shape of the object was presented. Zebrafish showed discrimination for color, shape, and color+shape combined, but not size. These results imply that zebrafish seem to use some categorical system to discriminate items, and distracters affect their ability for discrimination. The type of variables available (color and shape) may favor zebrafish objects perception and facilitate discrimination processing. We suggest that this easy and simple memory test could serve as a useful screening tool for cognitive dysfunction and neurotoxicological studies.

This study aimed to test seeking behavior caused by alcohol and the drug effects on learning in the zebrafish, Danio rerio. Three treatments were conducted: acute, chronic and withdrawal, using 0.10%, 0.25%, and 1.00% alcohol and control (0.00%) (vol/vol.%). For the drug seeking behavior, we used a place preference paradigm (shuttle box tank) before and after alcohol exposure in acute (single exposure) and chronic (7 days) treatments. We observed a change in the basal preference due to the association with alcohol only for 0.25% and 1.00% doses in both acute and chronic offering, indicating an alcohol-seeking behavior after the drug exposure. For the learning task, two treatments were tested: chronic alcohol exposure (26 days including the learning period) and alcohol withdrawal (15 days of alcohol exposure before the learning period). During the learning period, fish received light stimulus followed by food in a pre-defined area of the tank for 8 consecutive days. The low dose group (0.10%) learned the task by the 3rd day both in chronic and withdrawal treatments. The higher doses (0.25% and 1.00%) caused a learning impairment in the chronic treatment group, while fish from the alcohol withdrawal treatment displayed learning on the final testing day. Therefore, we suggest that high alcohol doses impair learning and cause drug seeking behavior, even after drug exposure cessation, while low doses positively affect learning and do not cause seeking behavior. Given our results we propose that the zebrafish is a promising model for identifying active compounds, antibodies or genes which modulate the alcohol dual effects: learning improvement and reinforcing behavior.

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The present study tested the effects of alcohol on seeking behavior and memory in the Siamese fighting fish Betta splendens. We tested behavior using 5 alcohol concentrations: .00%, .10%, .25%, 1.00%, and 1.50% (vol/vol%). Drug seeking was tested using a conditioned place preference (CPP) paradigm, with a single 20-min exposure to alcohol. The effect of alcohol on memory was tested using a T-maze protocol with acute (20 min/day for 5 days) and chronic (20 min/day for 20 days) alcohol exposure and after alcohol withdrawal (20 min/day alcohol exposure for 15 days ϩ water exposure). In the CPP test, the higher acute alcohol doses (1.00 and 1.50%) induced seeking behavior, but the lower (.10%) and medium (.25%) doses did not. When the fish were tested after 37 days of alcohol exposure, the higher-dose groups still exhibited seeking behavior, indicating that these doses may have caused drug addiction. In the memory test, we observed a dose-dependent pattern with both the acute and chronic treatments. High alcohol doses (1.00 and 1.50%) impaired memory, and low alcohol doses (.10%) caused an anticipatory response. The withdrawal group did not exhibit differences in memory, suggesting some capacity for recovery. The low alcohol doses did not impair memory or cause drug seeking, whereas the high doses affected memory and caused prolonged seeking behavior. Therefore, a dual effect of alcohol was corroborated by our data, and Betta splendens may be an adequate animal model for high-throughput screening with alcohol.