Developmental Changes in the Activation of Signal Transduction Pathway via JNK in Rat Hippocampus after Kainic Acid-Induced Seizure / 신경정신의학

ABSTRACT

OBJECTIVE: We observed the developmental pattern of activation of MAPK signal transduction pathways known to be activated by electroconvulsive shock(ECS) in young rat hippocampus after kainic acid(KA)-induced seizure. METHODS: We used the method of immunoblotting for examining the basal protein amount and basal level of phosphorylation of MAPK kinase(SAPK/ERK kinase -1, SEK-1), MAPK(c-Jun N terminal protein kinase, JNK), transcription factor(c-Jun) and immediate early gene proteins(Fos) in rat hippocampus at postnatal day 7, 14, and 21, respectively. We also examined the changes of phosphorylation of those proteins after kainic acid-induced seizure in the same way. RESULTS: The basal protein amounts of SEK-1, JNK, and c-Jun did not show age-dependent changes and basal level of phosphorylation of JNK and c-Jun remains unchanged throughout the early developmental period. The basal level of phosphorylation of SEK-1 was peaked at postnatal 7 days and then decreased with aging. After kainic acid-induced seizure, the change of phosphorylation of JNK was not observed but those of SEK-1 and c-Jun increased after postnatal day 14. The expression of Fos was observed at postnatal day 7 and also increased with aging. CONCLUSION: These results show that the MAPK signal transduction system in rat hippocampus matures in accordance with aging, but the process of maturation differs depending specific proteins. This study suggests the signal transduction cascade(SEK-1 - JNK - c-Jun - Fos) which is well established in cell line studies may not be applied to rat hipposcampus because we could not observe the activation of JNK after KA-induced seizure in young rat hippocampus.