Incorporation of PCB in the diet of pregnant rats has been shown to alter the thyroid status of offspring, as well as maternal behavior and pup behavior. In an effort to tease apart prenatal and postnatal PCB influence, in the present study pups either remained with their control (normal diet) or PCB fed (25 mg PCB 47/77 mixture/kg diet) dam, or were cross-fostered to a dam of the opposite dietary treatment. Rat pup behavior was determined on postnatal day (PND) 10 (isolation ultrasonic vocalization, USV), PND 12-14 (conditioned odor preference for the dam, COP), PND 15-17 (grooming syntax), and PND 15-16 (open field behavior). Serum thyroxine concentrations were determined on PND 17.
PCB significantly depressed thyroxine concentrations in a predictable fashion, with that of pups remaining with PCB dams depressed the most (35%), and those cross-fostered in either direction an intermediate amount (15%) as compared with pups remaining with control dams. Exposure to PCB increased the number per time of USV (69%) and line crosses in the open field (122%) regardless of cross fostering. Additionally, grooming behavior was disrupted most significantly on PND 16. Pups remaining with the PCB dams had the lowest rate of completed grooming chains (19%) followed by pups that were born to a PCB dam and then cross-fostered to a control dam (27%). Pups remaining with control dams had the highest rate of grooming chain completion (42%). During COP testing, controls failed to show a preference for the presence or absence of a lemon scent when paired with the dam or a cotton ball. In contrast, pups exposed to PCB showed a strong aversion to lemon scent, spending only 29% of their time near it, regardless of whether it was paired with the dam or a cotton ball. Taken together, these data suggest that the combination of exposure to small amounts of PCB and differences in maternal care causes altered development of behavioral measures, regardless of its influence on thyroid status or whether exposure occurs in the perinatal period during gestation only, lactation only, or both.