The effects of kainate-induced Seizure on the Opioid Peptide Gene Expression in Rat Hippocampus

ABSTRACT

In the rat hippocampal formation, the time-course and dose-response of the expression of enkephalin and dynorphin gene were examined after kainate (KA) treatment with in situ hybridization histochemistry. The KA induced enkephalin and dynorphin mRNA expression in hippocampus occurred mainly in the dentate gyrus. The enkephalin mRNA expression appeared at 3hour after KA injection, increased dramatically at 6hour, and then decreses. At 24hour after KA injection, the expression of enkephalin mRNA disappeared. The dynorphin mRNA expression appeared at once after injection and increased dramatically at 3hour. Unexpectedly at 6hour after injection, the expression was decreased, and then increased less than the 3hour expression. The increased pattern persisted to 24hour after injection. Unexpected result was also encounted in the experiment of KA dose-response of enkephalin mRNA and dynorphin mRNA. In the hippocampal formation, in contrast with other areas, low dosage (8mg/kg) of KA induced more significant expression of both genes than high dosage (16mg/kg) of KA.