Dynamics of microglial cells in the brain of Ihara epileptic rats in accordance with seizure progress

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It is supposed that the significance of glial reaction in epileptic brain might be unveiled by clarify the localization and degree of gliosis in epileptic mutant, Ihara epileptic rat. Possible function of microglia cells in the rat experienced epileptic seizures was studied by investigation of localization and degree of microglial reaction in IER brains with immunohitochemical examination using OX-42 antibody. Density of OX-42 positive microglial cells was investigated in the portions of cerebral cortex, endorrhinal cortex, thalamus, amygdale, hippocampus and dentate gyrus in IERs and non-epileptic control rats.In IERs, rats of 2 months old, microglial with OX-42 positive reaction was increased in mild or moderate degree in the portions of the brain described above, particularly in the hippocampus, the thalamus and the amygdala. In rats of 6 months and 10 months old, marked increase in OX-42 positive microglia was found in hippocampus, thalamus and amygdala in addition to the whole brain. Microglia cells with OX-42 positive reaction, which possessed short and thick processes, were thought to be an activated microglial of amoeboid type.It is suggested that microglial activation was induced by epileptic activities in the brain of IER, and then cytokines released by activated glial cells have some influences to the functions of neurons or glial cells. Because increased activated microglia was shown in the portions of hippocampus, thalamus and amygdala from young age, those areas ware thought to have significant role for the epileptogenesis. Furthermore, it is safely assumed that epileptic activities influenced not only in the hippocampus, thalamus and amygdala but also in other portions of the brain from the finding of diffuse increase in OX-42 positive cells in the whole brain of IER.