LACK OF EFFECT OF 3,3'4,4',5-PENTACHLOROBIPHENYL (PCB 126) THROUGHOUTGESTATION AND LACTATION ON MULTIPLE FIXED-INTERVAL FIXED-RATIO AND DRL PERFORMANCE IN RATS

There is evidence that polychlorinated biphenyl (PCB) congeners have d ifferential effects on endpoints of neurotoxicity depending on their c hemical structure:specifically, that ortho-substituted congeners are n eurotoxic while coplanar (dioxin-like) congeners are relatively inacti ve 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 wi th 0, 0.25, or 1 mu g/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week bree ding period produced 10, 7, and 13 litters in the three dose groups, r espectively, used in behavioral assessment. Breeding females from the control and Iow-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 i nterval-fixed ratio schedule of reinforcement beginning at about 200 d ays of age, followed immediately by performance on a DRL schedule. The re were no compelling indications of a treatment-related effect on eit her 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 c ohorts. These data provide further evidence for absence of behavioral toxicity as a result of gestational and lactational exposure to dioxin -like PCB congener. Published by Elsevier Science Inc.