Expressions of the pERK1/2 and the cFos Proteins at an Early Stage of Transient Global Ischemia-reperfusion Injury in the Hippocampus of Rats

ABSTRACT

PURPOSE: This study was to evaluate temporal changes in the expressions of the phosphorylated extracellular-regulated kinase1/2 (pERK1/2), the phosphorylated MAPK/ERK kinase1/2 (pMEK1/2) and the cFos proteins in the hippocampus of rats following transient global ischemia. METHODS: Transient global ischemia was induced in the forebrains of Sprague-Dawley rats by using a 4-vessel occlusion for 20 min under anesthetic condition. Hematoxyline-eosin staining showed typical microscopic findings that represented neuronal cell death in hippocampal CA1 regions 5 days after transient global ischemia. Four-vessel occlusion-reperfusion produced ischemic injury in major forebrain structures, such as the striatum, the cortex and the hippocampus, in the finding of triphenyltetrazolium chloride (TTC) staining. RESULTS: A high density of pERK1/2 immunoreactivity existed in the pyramidal-cell layers of the CA2-3 regions and in the granular-cell layers of the dentate gyrus 5 min after ischemia. Following ischemia, expression of the pMEK1/2 protein showed temporal changes similar to that of the pERK1/2 protein. A significant expression of the cFos protein was noted in the pyramidal-cell layers of the CA2-3 regions and in the granular-cell layers of the dentate gyrus 2 hours after global ischemia. CONCLUSION: Intracellular signaling cascades of the ERK or the cFos protein take part in early cellular events in the hippocampus of rats in response to ischemic insult.