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DEVELOPMENTAL EXPOSURE TO POLYBROMINATED DIPHENYL ETHERS DOES IMPAIRS SYNAPTIC TRANSMISSION AND LTP IN HIPPOCAMPUS.
Citation:
Gilbert, M. E., L. Sui, AND K M. Crofton. DEVELOPMENTAL EXPOSURE TO POLYBROMINATED DIPHENYL ETHERS DOES IMPAIRS SYNAPTIC TRANSMISSION AND LTP IN HIPPOCAMPUS. Presented at Society of Toxicology, Baltimore, MD, 3/21-25/2004.
Description:
Polybrominated diphenyl ether (PBDE) flame retardants bioaccumulate in wildlife and in humans and reduce circulating levels of thyroxine (T4). The present work examined hippocampal function in adult offspring of LE rats treated daily by oral gavage with 0, 30 or 100 mg/kg of a commercial PBDE mixture, DE71 from gestational day 6 to weaning on postnatal day (PND) 21. This regimen produced moderate decreases in T4 (40-70%) during the early postnatal period with recovery to control levels by PND36. Spatial learning and hippocampal synaptic transmission were evaluated in adult male offspring. Learning was assessed in a Morris water maze (2 trials/day for 15 days). Several weeks later, electrodes were implanted in the perforant path and dentate gyrus under urethane anesthesia, to examine synaptic function. Input/output (I/O) and paired- pulse functions were collected to assess baseline synaptic transmission and short-term facilitation. Long-term potentiation (LTP) was induced by delivering theta burst stimulation at a modest (300uA)and a high (1500uA) stimulus intensity. No effect of DE71 was seen on spatial learning. In baseline I/O recordings, population spike amplitude was increased in the 100 mg/kg group relative to controls, with no effect on EPSP slope amplitude. LTP of the population spike was impaired in response to both stimulus strengths in the 100 mg/kg dose group. These data suggest that the reductions in T4 induced by DE71 were sufficient to alter synaptic transmission in the dentate gyrus of the hippocampus. Effects of DE71 on hippocampal synaptic function are similar to those produced by developmental exposure to the polychlorinated biphenyl mixture, A1254, which also failed to affect learning in the Morris water maze. Collectively, these results suggest that identifying behavioral correlates of subtle changes in hippocampal synaptic function may require more sophisticated tests of learning and memory. (This is an abstract of a proposed presentation and does not reflect US EPA policy).