Alterations in Neurobehavioral Responses in Fishes Exposed to Lead and Lead-chelating Agents

Abstract

Lead (Pb) is a neurotoxic element that causes behavioral dysfunction in fishes within days of exposure to sublethal concentrations. To test the hypothesis that internal stores of Pb have long-term behavioral effects, Pb-exposed (0.3 ppm) fish were either treated with the Pb-chelating drug meso-2,3 dimercaptosuccinic acid (DMSA) or returned to controlconditions (0.0 ppm Pb). Swimming capacity improved after a 7-day DMSA (1.5 ppm) exposure (ANOVA P < 0.05). Removing fish from conditions of waterborne Pb did not achieve this result; DMSA alone without Pb pretreatment had no significant effect. Blood Pb (BPb) levels in control or DMSA-only fish were not detectable. Treated groups had significantly higher BPb (ANOVA, P < 0.05): Pb-exposed fish—530.5 ± 156.7, 884.6 ± 130.0 ppm (1, 2 wks, respectively); Pb-exposed → 0.0 ppm water—488.8 ± 67.3 ppm after 2 wks; Pb-exposed → 1.5 ppm DMSA—202.0 ± 116.0 ppm after 2 wks. Norepinephrine and vanillylmandelic acid levels were altered by Pb exposure (ANOVA, P < 0.05). Whereas removing Pb did not facilitate a return to control values, adding DMSA did (ANOVA, P < 0.05). Temporal-spatial response patterns to a stimulus in Pb-exposed (0.1 ppm) and Pb-exposed → 0.0 ppm Pb water groups differed from controls (0.0 ppm Pb; 0.0 ppm DMSA) for stimulus response angle, and rate and extent of movement away from stimulus source. While the two control types were similar for stimulus response angle and reaction time, DMSA-only controls, unlike 0.0 ppm Pb controls, did not respond as a tightly-associated group after the stimulus.