Epileptogenesis causes an N-methyl-d-aspartate receptor/Ca2+-dependent decrease in Ca2+/calmodulin-dependent protein kinase II activity in a hippocampal neuronal culture model of spontaneous recurrent epileptiform discharges

摘要

Alterations in the function of Ca²⁺/calmodulin-dependent protein kinase II (CaM Kinase II) have been observed in both in vivo and in vitro models of epileptogenesis; however the molecular mechanism mediating the effects of epileptogenesis on CaM Kinase II have not been elucidated. This study was initiated to evaluate the molecular pathways involved in causing the long lasting decrease in CaM Kinase II activity in the hippocampal neuronal culture model of low Mg²⁺ induced spontaneous recurrent epileptiform discharges (SREDs). We show here that the decrease in CaM kinase II activity associated with SREDs in hippocampal cultures involves a Ca²⁺/N-methyl-d-aspartate (NMDA) receptor-dependent mechanism. Low Mg²⁺ induced SREDs results in a significant decrease in Ca²⁺/calmodulin-dependent substrate phosphorylation of the synthetic peptide autocamtide-2. Reduction of extracellular Ca²⁺ levels (0.2 mM in treatment solution) or the addition of DL-2-amino-5-phosphonovaleric acid (APV) 25 µM blocked the low Mg²⁺ induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid receptor or L-type voltage sensitive Ca²⁺ channel had no effect on the low Mg²⁺ induced decrease in CaM kinase II-dependent substrate phosphorylation. The results of this study demonstrate that the decrease in CaM kinase II activity associated with this model of epileptogenesis involves a selective Ca²⁺/NMDA receptor-dependent mechanism and may contribute to the production and maintenance of SREDs in this model.