Lack of Effect of 3,3′4,4′,5-Pentachlorobiphenyl (PCB 126) Throughout Gestation and Lactation on Multiple Fixed Interval–Fixed Ratio and DRL Performance in Rats

There is evidence that polychlorinated biphenyl (PCB) congeners have differential effects on endpoints of neurotoxicity depending on their chemical structure: specifically, that ortho-substituted congeners are neurotoxic while coplanar (dioxin-like) congeners are relatively inactive in producing neurotoxic effects. This study extends research on the effects of developmental exposure to the coplanar congener 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) in Long–Evans rats. Dams were dosed with 0, 0.25, or 1 μg/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week breeding period produced 10, 7, and 13 litters in the three dose groups, respectively, used in behavioral assessment. Breeding females from the control and low-dose group that did not conceive were rebred after 76 days of dosing, producing 6 and 6 litters used in behavioral testing. One female and male from each litter were tested on a multiple fixed interval–fixed ratio schedule of reinforcement beginning at about 200 days of age, followed immediately by performance on a DRL schedule. There were no compelling indications of a treatment-related effect on either schedule. These same rats failed to exhibit PCB-induced impairment on a spatial delayed alternation task performed prior to the current experiments. This regimen of PCB exposure produced reduced weight gain between birth and weaning in Cohort 1, and decreased thyroxine levels and changes in hematology and serum biochemistry parameters in both cohorts. These data provide further evidence for absence of behavioral toxicity as a result of gestational and lactational exposure to a dioxin-like PCB congener. Published by Elsevier Science Inc.