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.
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 has 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 result 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 microM blocked the low Mg2+-induced decrease in CaM kinase II-dependent substrate phosphorylation. Antagonists of the alpha-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.
Blair
Robert E
RE
Department of Neurology, Virginia Commonwealth University, School of Medicine, Richmond, Virginia 23298-0599, United States. rblair@vcu.edu
Sombati
Sompong
S
Churn
Severn B
SB
Delorenzo
Robert J
RJ
D000818:Animals; D002118:Calcium / Q000502:physiology*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D002478:Cells, Cultured; D002482:Cellulose / Q000031:analogs & derivatives; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004827:Epilepsy / Q000139:chemically induced* / Q000503:physiopathology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D007150:Immunohistochemistry; D008275:Magnesium Deficiency / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology*; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D012008:Recurrence; D013226:Status Epilepticus / Q000503:physiopathology
D004791:Enzyme Inhibitors; D016194:Receptors, N-Methyl-D-Aspartate; D019319:Okadaic Acid; D002482:Cellulose; C008881:phosphocellulose; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D002118:Calcium