Brief Postnatal PBDE Exposure Alters Learning and the Cholinergic Modulation of Attention in Rats
Polybrominated diphenyl ethers (PBDEs), chemicals commonly used as flame retardants, are ubiquitous in the environment and bioaccumulate in humans and wildlife. However, little is known about their potential toxicological properties. In the present study, male Long-Evans rats orally administered the commercial PBDE mixture DE-71 or corn oil for 1 week, beginning at postnatal day (PND) 6, were tested on a visual discrimination task and two sustained attention tasks. After completion of these tasks, the rats were administered a drug challenge with the muscarinic antagonist scopolamine (0, 0.01, 0.03, 0.05 mg/kg), which was injected subcutaneously 30 min prior to testing on the second sustained attention task. The DE-71–exposed rats demonstrated deficits in learning but not in sustained attention when compared to controls. Scopolamine impaired the animals' ability to detect the brief visual cues in controls, as evidenced by decreases in accuracy and increases in omission errors. However, the DE-71–exposed rats were subsensitive to the effects of scopolamine on omission errors, particularly on trials in which a long delay preceded the cue, suggesting alterations in the cholinergic modulation of sustained attention. For the DE-71–exposed rats, the lack of sustained attention deficits in the absence of the drug, coupled with the subsensitivity to scopolamine's effects on sustained attention, suggest that although this PBDE mixture produced lasting alterations in cholinergic functioning, either (1) these alterations were not of sufficient magnitude to be behaviorally relevant, or (2) behavioral deficits resulting from these alterations were overcome by the development of compensatory neural mechanisms or response strategies in adulthood.