ToxSci Advance Access originally published online on November 29, 2005
Toxicological Sciences 2006 89(2):415-422; doi:10.1093/toxsci/kfj051
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Auditory Deficits in Rats Exposed to an Environmental PCB Mixture during Development


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* Neuroscience Program, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61802;
Department of Psychology, College of Charleston, Charleston, South Carolina, 29424;
Center for Clinical Research and Evidence-Based Medicine, University of Texas Health Science Center at Houston Medical School, Houston, Texas, 77030; and
Department of Veterinary Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61802
Received August 22, 2005; accepted October 30, 2005
Previous studies have indicated that developmental exposure to polychlorinated biphenyls (PCBs) may result in hearing impairment in rats. The cochlea is the suggested site of action, based upon one study demonstrating a loss of outer hair cells on the basilar membrane, and another demonstrating deficits in distortion product otoacoustic emissions (DPOAEs). The current study was conducted to assess the possible ototoxic effects of a unique PCB mixture formulated to model the congener profile of PCBs found in fish consumed by a human population in northeastern Wisconsin. Female Long-Evans rats were dosed orally with the PCB mixture beginning 28 days prior to breeding and continuing until the pups were weaned. Dams were fed one-half of a cookie onto which was pipetted 0, 1, 3, or 6 mg/kg of the PCB mixture dissolved in a corn oil vehicle. On postnatal day (PND) 21, pups were weaned, and one male and one female from each litter were randomly selected for auditory assessment. DPOAEs were measured to assess cochlear function, and auditory brainstem responses (ABRs) were measured to determine effects on central nervous system auditory pathways. DPOAE amplitudes were decreased, and DPOAE and ABR thresholds were elevated across a range of frequencies in PCB-exposed rats. These results support and extend previous reports of auditory impairment in PCB-exposed rats. Developmental exposure to PCBs may also result in subtle auditory impairments in humans, and if so, this may contribute to some of the cognitive deficits that have been observed in epidemiological studies.
Key Words: PCBs; auditory system; DPOAE; ABR.