Effects of environmental stresses on the permeability of blood brain barrier

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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is considered to be one of the most potent environmental endocrine disruptors. TCDD has been demonstrated to be a potent carcinogen and have immunotoxic effects. It is still uncertain, however, whether dioxins have also toxic properties in the central nervous system. The present study was designed to investigate the toxicity of the subchronic treatment of TCDD in the central nervous system of male Wistar rats. Rats were received oral administrations of TCDD (1μg/kg/week) from 8 weeks-old to 28 weeks-old, and the locomotor activities, food consumption and water intakes were measured. The TCDD-treated rats were significantly reduced in the gains of body weight from 4 weeks after the administration, compared to vehicle-controls. Under 12 hour-light/dark condition, the TCDD-treated rats exhibited higher locomotor activities in all experimental periods, and that was statistically significant at 16-20 weeks after the treatment, without altering circadian rhythm. Food and water intakes were not different between the groups. These results suggest that TCDD may affect in a central nervous system to occur hyperactivity in rats even in adulthood.We examined, furthermore, the effects of stress on the permeability of blood brain barrier (BBB) using a communication box method. Rats were divided into three groups, namely, psychological stress, physical stress and control group. Permeability of BBB was examined by measuring the concentration of evans blue administered I.V., in the brain tissues. A load of stress increased the concentration of evans blue in cerebral cortex. This effect was more potent in a psychological stress group. In the hippocampus, both stresses also intend to increase the concentration of evans blue. These results suggest that TCDD induced hyperactivity in rat may more evident in case of stressful conditions.