Effects of noise pollution stress during pregnancy on anatomical and functional brain cortex development of the offsprings of NMRI mice

  Introduction: Effects of stress on changes in neural system activity is well defined, which might be because of the changes in brain cortex architecture. In the present study, the effects of maternal noise stress on the morphological and functional changes in brain cortex of off springs of NMRI mice were examined.   Materials and Methods: Female pregnant mice divided into two groups. Control group was maintained in their home cages without any invasion but the experimental group was exposed to the noise stress (80 db for 5 min/day) from day zero of pregnancy to day 14 (i.e. 15 days). After delivery, six pups from each group were killed and their brains were fixed, sectioned and stained in H;E. These sections were investigated by MOTIC software for both control and experimental groups. Other pups were nursed by their mothers until their adolescence (22 g-8 weeks old). Then they were examined for behavioral side-biased and locomotor activity tests.   Results: Decrease in cortex diameter and diameter of each layer for the experimental group was observed. In addition, neuron counting in each layer indicated that the number of the neurons in the middle and outer layers of cortex for the experimental group was reduced than the control group. In contrast, the number of the neurons in the inner layer of the experimental group was increased. From the functional view, in experimental group increases in left-handness especially in female off springs were observed. Furthermore, spontaneous locomotor activity in the new environment was increased in the experimental group. Conclusion: These results indicated that neuronal immigration and network connections in the inner layer of cortex through the middle and outer layers in the experimental group were inhibited. In other word, noise stress was able to inhibit brain cortex development in next generation