Seizure-induced changes of mineralocorticoid and glucocorticoid receptors in the hippocampus in seizure sensitive gerbils

Abnormal corticosteroid hormone levels during stress and resultant mineralocorticoid receptor (MR)/glucocorticoid receptor (GR) imbalance enhance the vulnerability of specific hippocampal neurons. In the present study, we investigated the distribution of MR and GR in seizure resistant (SR) and seizure sensitive (SS) gerbils, and observed the seizure-induced changes of MR and GR in the hippocampus of SS gerbils using immunohistochemistry and western blot analysis. MR and GR immunoreactivities were higher in the SS pre-seizure gerbils than that in SR gerbils. In the SR gerbils, the immunodensity of GR was high compared to that of MR. The changes of MR and GR immunoreactivities were significant in the stratum pyramidale of the hippocampal CA1 region and the infrablade of the dentate gyrus after seizure on-set. MR immunoreactivity in the CA1 region was significantly increased at 12 h after seizure on-set, thereafter MR immunoreactivity was decreased. MR immunoreactivity in the dentate gyrus was decreased time-dependently after seizure on-set. GR immunoreactivity was decreased in the CA1 region and dentate gyrus time-dependently after seizure on-set. At 12 h after seizure on-set, differences in MR and GR immunodensity diminished in the CA1 region and dentate gyrus. This imbalance of MR and GR immunoreactivity in these regions may be associated with seizure generation in the Mongolian gerbil, which is a hereditary seizure model.