The motor activity behavior of fish (mirror carp) was investigated in an open field test following lead exposure (50 µg/l) for a period of 30 days. Lead is a highly toxic heavy metal, which affects the nervous system in particular. Exposure to lead has been associated with behavioral disorders (such as movement anomalies), learning impairments, memory loss and cognitive functional damages in humans and experimental animals. Behavioral correlates of oxidative damage in the brain, identified as lipid peroxidation, have been found in a number of neurological and neuropsychiatric disorders.

For these open field behavior tests, the floor of an aquarium was divided into a grid of 1 inch squares, and the side walls were divided horizontally by lines at 3 inch intervals. A fish that moved from one grid square to the next was given a score of one; a fish crossing a horizontal line on the side of the tank scored two; and any fish moving up or down by half its length also received a score of one. These motor behaviors were scored every day at 09:00 for two minutes, taking the mean of all scores from two individual sets of fish.

During the first week of lead exposure, the fish showed jerky behavior and/or quick motor activity behavior. However, the movements of most fish were relatively stable, with no appreciable increase or decrease in their motor activities. Spontaneous increases in the movement behavior of these fish were observed between days 16 and 30 of lead exposure, with a maximum of 129% at the end of the experiment. Lipid peroxidation in their brains had increased by 52% by day 15 and 156% by day 30.

This study indicates that increased levels of lipid peroxidation were found in the brains of fish showing anomalies in motor activity during chronic lead exposure.

Paper presented at Measuring Behavior 2002 , 4^th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands

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