Gender-dependent behavioral and sensory effects of a commercial mixture of polychlorinated biphenyls (Aroclor 1254) in rats.

Developmental exposure to polychlorinated biphenyls (PCBs) has been associated with behavioral and cognitive deficits in humans and animal models. Perinatal exposure to PCBs has also been associated with sensory deficits in animal models. These effects were hypothesized to be mediated in part by ortho-substituted PCBs, which do not or weakly bind to the aryl hydrocarbon (Ah) receptor. The present studies were designed to determine whether perinatal exposure to Aroclor 1254, a commercial mixture of > 99% ortho-substituted PCBs, would affect cognitive and sensory function in Long-Evans rats. Adult male and female offspring of female rats fed Aroclor 1254 (Lot #124-191; doses of 0, 1, or 6 mg/kg/day; gestational day 6 through postnatal day 21; n = eight/group) were trained to perform a signal detection task capable of assessing sensory thresholds. Training included autoshaping and operant conditioning. Thresholds for detecting a 1-s light stimulus were determined under background illuminations ranging from 2 lux to complete darkness. Female rats exposed to Aroclor 1254 autoshaped more rapidly than control females, at a rate akin to control males. Control females had lower thresholds than control males at all levels of background illumination. These differences were abolished by Aroclor 1254, which reduced thresholds in males and increased thresholds in females. These data extend previous findings of gender-specific effects of PCBs on neurobehavioral development to measures of acquisition and sensory function.