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DEVELOPMENTAL EXPOSURE TO POLYBROMINATED DIPHENYL ETHERS DOES NOT ALTER SYNAPTIC TRANSMISSION AND LTP IN HIPPOCAMPUS.
Citation:
Gilbert, M. E. AND K M. Crofton. DEVELOPMENTAL EXPOSURE TO POLYBROMINATED DIPHENYL ETHERS DOES NOT ALTER SYNAPTIC TRANSMISSION AND LTP IN HIPPOCAMPUS. Presented at Society of Toxicology, Nashville, TN, March 17-21, 2002.
Description:
Polybrominated diphenyl ether (PDE) flame retardants bioaccumulate in the environment, in wildlife, and in humans. Concern has been raised over potential thyrotoxic effects of this class of xenobiotics. Severe hypothyroidism during critical periods of brain development leads to alterations in hippocampal structure and physiology and produces learning deficits. The present work examined field potentials evoked in the dentate gyrus of adult offspring of dams treated daily with 0 or 30 mg/kg of DE71, a commercial PDE mixture, from gestational day 6 to weaning at postnatal day (PND) 21. This regimen produced moderate decreases (~55%)in thyroxine (T4) during the early postnatal period that returned to control levels by PND36. Triiodothyronine (T3) was unaffected. Male offspring(4-8 mon)were anesthetized with urethane and electrodes implanted in the perforant path and dentate gyrus. Input/output (I/O) functions were collected to assess the integrity of synaptic transmission. Long-term potentiation (LTP) was induced by delivering theta burst stimulation at a modest stimulus intensity of 300 A and I/O functions were re-evaluated 1 hr later. Thereafter, a second set of trains at maximal stimulus intensity (1500 A) was administered and a third I/O collected 15 min later. No alterations in population spike, EPSP slope, or postsynaptic potential amplitudes were observed in baseline I/O recordings of DE71-treated animals relative to controls. Modest LTP was observed in both groups in response to the low intensity train stimulation, and robust LTP was induced by the higher intensity train series. No group differences in LTP magnitude were revealed. The lack of effects of PDE differs from the response to either propylthiouracil or A1254, agents that also transiently reduce thyroid hormones during development, albeit it to a greater degree. These data suggest that the modest reductions in T4 induced by this dosing regimen with DE71 were not sufficient to alter synaptic transmission in the dentate gyrus of the hippocampus. (Does not reflect US EPA policy).