title: Epileptiform discharge upregulates p-ERK1/2, growth-associated protein 43 and synaptophysin in cultured rat hippocampal neurons.
abstract: Extracellular signal-regulated protein kinase, ERK1/2 is activated by phosphorylation (p-ERK1/2) during environmental stress such as epileptiform discharge. We investigated the role of ERK1/2 in abnormal axon growth and synapse reorganization in cultured neurons displaying epileptiform activity. The cultured neurons displaying epileptiform activity were treated with magnesium-free extracellular fluid for 3h and monitored epileptiform discharges using whole-cell patch clamp. Two study groups, neurons displaying epileptiform activity and the same neurons treated with ERK1/2 inhibitor U0126, were studied at six time points, 0 min, 30 min, 2h, 6h, 12h, and 24h following discharge. The expressions of p-ERK1/2, C-fos, growth-associated protein 43 (GAP-43) and synaptophysin (SYP), as markers of axon growth and synapse reorganization, were investigated by double-label immunofluorescence and western blotting. In the neurons displaying epileptiform activity, p-ERK1/2 was detected immediately following discharge, and expression peaked at 30 min. The expression of C-fos, GAP-43 and SYP followed the same pattern as p-ERK1/2. In the treated group, p-ERK1/2 was inhibited completely, and C-fos, GAP-43 and SYP were reduced. These findings indicate that epileptiform discharge activates ERK1/2 which regulates C-fos in cultured neurons displaying epileptiform activity, and this cascade may upregulate GAP-43 and SYP to contribute to axon growth and synapse reorganization to potentiate epileptic activities.
authors.affiliation: Department of Neurology, the Second Affiliated Hospital, Chongqing Medical University, Chongqing 400010, China.
authors.forename: Zu-Cai
authors.initials: ZC
authors.lastname: Xu
authors.forename: Yang-Mei
authors.initials: YM
authors.lastname: Chen
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.forename: Yun-Lan
authors.initials: YL
authors.lastname: Xie
authors.forename: Ke-Bin
authors.initials: KB
authors.lastname: Zeng
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D019922:GAP-43 Protein / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology*; D008274:Magnesium / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D016708:Synaptophysin / Q000378:metabolism*; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019922:GAP-43 Protein; D016708:Synaptophysin; D048049:Extracellular Signal-Regulated MAP Kinases; D008274:Magnesium