Light microscope stereological study of cortical dysplasias in cerebral cortex and hippocampus of rat model

Abstract:

Objective：To observe the precise pathological characteristics（cerebral hemisphere and hippocampal volume，neuronal quantity and so on） of animal models of diffuse cortical dysplasias（DCD） in cortex with stereological methods，and to discuss the mechanism of pathologic changes and epileprogenesis in this model. Methods：An animal model of DCD was established by exposing pregnant SD rats to X ray using a single dose of 150 cGy on embryonic day 17（E17） for 84 seconds. Slice was followed by quantita－tive analysis of neuron density，cell，diameter of nucleus，the distribution（DCD） and white matter neurons using Gundersen two-di－mensional cell counting methods. Statistics analysis was used with mean standard deviation（x±s），P<0.05 representing significant，and student test analysis. Results：From birth to adult rats，the weight of body and brain of DCD rats decreased about 19%（P>0.05） and 57%（P<0.05） respectively. The volume of brain，cortex，hippocampus and CA1 decreased about 36%（P<0.05），19%（P>0.05），39%（P<0.05） and 32%（P<0.05） respectively，but only P56 and P84，compared with the same age group，decreased 38% and 36%（P<0.05） respectively. Cortex/brain，hippocam－pus/brain，and CA1/hippocampus decreased about 20%，21%and 27% respectively in DCD rats，but only P56 and P84 for CA1/hippocampus was significantly reduced by 37% and 35%（P<0.05）. HE stain and Nissl stain showed there were clusters of large neurons in both superficial and deep layers in the model rats’ cortex. Neuron density，cell density and neuron percentage increased 99 times，121 times，and 64 times respectively in DCD rats with statistical significance（P<0.05）. The average level of neuronal nuclei Feret’s diameter was not statistically significant. DCD rat brain，and hippocampal volume reduction lay mainly in coronal shortening. In DCD rat，ectopic nodules，subcortical heterotopic nodules and ectopic hippocampal structure and cell characteristics of nodules of cortical layer Ⅰ were similar compared with the cortical nod－ules of Ⅱ~Ⅲ cortex layer. Conclusion：DCD rat cortical section layerⅠ，subcortical white matter and hippocampus ectopic nodules did not migrate to the cortex layer Ⅱ~Ⅲ. Biological stereology method is a good approach to study and research biology because it can detect precise pathological characteristics.