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

Lead (Pb) is a neurotoxic element that causes behavioral dysfunctionin fishes within days of exposure to sublethal concentrations.To test the hypothesis that internal stores of Pb have long-termbehavioral effects, Pb-exposed (0.3 ppm) fish were either treatedwith the Pb-chelating drug meso-2,3 dimercaptosuccinic acid(DMSA) or returned to controlconditions (0.0 ppm Pb). Swimmingcapacity improved after a 7-day DMSA (1.5 ppm) exposure (ANOVAP < 0.05). Removing fish from conditions of waterborne Pbdid not achieve this result; DMSA alone without Pb pretreatmenthad no significant effect. Blood Pb (BPb) levels in controlor DMSA-only fish were not detectable. Treated groups had significantlyhigher 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 after2 wks; Pb-exposed 1.5 ppm DMSA—202.0 ± 116.0 ppmafter 2 wks. Norepinephrine and vanillylmandelic acid levelswere altered by Pb exposure (ANOVA, P < 0.05). Whereas removingPb did not facilitate a return to control values, adding DMSAdid (ANOVA, P < 0.05). Temporal-spatial response patternsto a stimulus in Pb-exposed (0.1 ppm) and Pb-exposed 0.0 ppmPb water groups differed from controls (0.0 ppm Pb; 0.0 ppmDMSA) for stimulus response angle, and rate and extent of movementaway from stimulus source. While the two control types weresimilar for stimulus response angle and reaction time, DMSA-onlycontrols, unlike 0.0 ppm Pb controls, did not respond as a tightly-associatedgroup after the stimulus.