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Results of the hole-board test: (a) general behavioral activity decreased by the end of week 6 in the exposed animals and increased in the controls; (b) number of head dips into holes sharply reduced by the end of the experiment in the exposed animals and was stable in the controls. The abscissa shows the exposure time in weeks, and the ordinate shows the value of the corresponding indicator; * compared with the controls; # compared with the value in the same group in week 1.
