Effects of 2,3,7,8-TeCDD during pregnancy on the neurodevelopment of rat fetuses and off-springs

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The effects of 2,3,7,8-TeCDD (TeCDD) during pregnancy on motor development and learning processes of rat off-springs were investigated in this study.TeCDD or corn oil was orally administered to pregnant rats during the 9^<th> - 19^<th> day of pregnancy. Both of exposed and control off-springs were fed with ad libitum access to maternal breast milk after birth, and to food and water after weaning. The following experiments were conducted and obtained the results.1. Effects of TeCDD on fetus brain : On day 19 of gestation, fetuses of 6 TeCDD group and 5 controls were removed from the uterus. Brains were collected from the fetuses and divided into three parts : the cerebrum, cerebellum, and hypothalamus. The rates of hypothalamus per whole brain of TeCDD group were significantly higher than those of controls.2. Effects of TeCDD on off-springs : From the 4^<th> to 14^<th> day after birth, measurement the time of turning around on the slope was performed to test motor development. The latent time of TeCDD group was significantly longer than that of controls during the 7^<th> to 11^<th> day in both sexes. Every day from the 31^<th> to 44^<th> day after birth, performance of avoidance behavior in a shuttle box was examined after conditioning with a tone and electric shock. Improvement of escape rates and escape latent periods during these days was delayed in TeCDD group as compared with that of controls in male rats. Also lower spontaneous activity was observed in TeCDD exposed male rats. The increased rates of hypothalamus per whole brain of TeCDD group were also recognized in anatomical investigations after behavior examinations.These results suggest that TeCDD exposure during pregnancy affect neurodevelopment of off-springs during growth period, especially in male rats.