Developmental exposure of rats to a reconstituted PCB mixture or aroclor 1254: Effects on long-term potentiation and [H-3]MK-801 binding in occipitalcortex and hippocampus

The central nervous system is one of the target organs for polychlorinated biphenyls (PCBs), We measured the effects of maternal exposure of Long-Evan s rats to a mixture of PCB congeners reconstituted according to the pattern found in human breast milk (reconstituted mixture, RM) on long-term potent iation (LTP) in two brain regions. Exposure of the dams via food started 50 days prior to mating and was terminated at birth, In the first experiment, adult male and female offspring were exposed maternally to 40 mg/kg of the RM or the commercial mixture Aroclor 1254 (A1254), LTP and paired-pulse in hibition were measured in slices of the visual cortex. In addition, the bin ding of [H-3]MK-801 to the N-methyl-D-aspartate (NMDA) receptor-ion channel as well as the [H-3]muscimol binding to the GABA-A receptor in membrane pr eparations from the occipital cortex and hippocampus were determined. LTP a s well as [H-3]MK-801 binding were significantly reduced in the cortex foll owing PCB exposure, while [H-3]MK-801 binding in the hippocampus was not af fected. In a succeeding experiment, LTP was determined in cortical and hipp ocampal slices from rats at postnatal days 10 to 20, following exposure to 0, 5, or 40 mg/kg of the RM, Cortical LTP was significantly affected by the RM while no effects were seen in hippocampal LTP, Taking the two experimen ts together, PCB exposure significantly reduced LTP, as well as [H-3]MK-801 binding, in the cortex and had no effect in the hippocampus. The LTP defic its can only partly be related to the reduction of binding sites to the NMD A receptor; other PCB-induced neurochemical changes have to be assumed.