Regional alterations in serotonin metabolism induced by oral exposure of rats to polychlorinated biphenyls.

Adult male rats were gavaged with a mixture of Aroclors 1254 and 1260 at a dose level of either 500 or 1000 mg/kg and were killed on post-gavage days 1, 3, 7 and 14. Total PCB concentrations and concentrations of serotonin and its major central metabolite, 5-hydroxyindoleacetic acid, were determined in the dorsal frontal cortex, lateral olfactory tract, hippocampus, medial-basal hypothalamus and brainstem. Differences in the initial concentrations and redistribution patterns of PCBs were observed in the brain regions examined. Serotonin concentrations were reduced in frontal cortex and hippocampus, unaffected in hypothalamus and brainstem and elevated in lateral olfactory tract. Serotonin metabolism, estimated by determination of the metabolite to neurotransmitter ratio, was elevated in all brain areas except for the lateral olfactory tract. These results demonstrate that following a single exposure to PCBs, there are significant changes in serotonin concentrations and metabolism in the adult rat. Furthermore, there are regional brain differences with regard to PCB concentrations and the direction and magnitude of neurochemical change induced by the PCBs.