dizocilpine-maleate and syntide-2

The development of symptomatic epilepsy is a model of long-term plasticity changes in the central nervous system. The rat pilocarpine model of epilepsy was utilized to study persistent alterations in calcium/calmodulin-dependent kinase II (CaM kinase II) activity associated with epileptogenesis. CaM kinase II-dependent substrate phosphorylation and autophosphorylation were significantly inhibited for up to 6 weeks following epileptogenesis in both the cortex and hippocampus, but not in the cerebellum. The net decrease in CaM kinase II autophosphorylation and substrate phosphorylation was shown to be due to decreased kinase activity and not due to increased phosphatase activity. The inhibition in CaM kinase II activity and the development of epilepsy were blocked by pretreating seizure rats with MK-801 indicating that the long-lasting decrease in CaM kinase II activity was dependent on N-methyl-D-aspartate receptor activation. In addition, the inhibition of CaM kinase II activity was associated in time and regional localization with the development of spontaneous recurrent seizure activity. The decrease in enzyme activity was not attributed to a decrease in the alpha or beta kinase subunit protein expression level. Thus, the significant inhibition of the enzyme occurred without changes in kinase protein expression, suggesting a long-lasting, post-translational modification of the enzyme. This is the first published report of a persistent, post-translational alteration of CaM kinase II activity in a model of epilepsy characterized by spontaneous recurrent seizure activity.

Topics: Animals; Brain; Calcium-Calmodulin-Dependent Protein Kinases; Dizocilpine Maleate; Enzyme Inhibitors; Excitatory Amino Acid Antagonists; Intercellular Signaling Peptides and Proteins; Isoenzymes; Male; Okadaic Acid; Peptides; Phosphoric Monoester Hydrolases; Phosphorylation; Pilocarpine; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Secondary Prevention; Seizures; Status Epilepticus; Time Factors

Neurotoxic effects of excitatory amino acids have been implicated in various neurological disorders, and have been utilized for excitotoxic models of delayed neuronal cell death. The excitotoxic glutamate-induced, delayed neuronal cell death also results in inhibition of calcium/calmodulin-dependent kinase II (CaM kinase II). In this report, we characterized the glutamate-induced inhibition of CaM kinase II in relation to loss of intracellular calcium regulation and delayed neuronal cell death. Glutamate (500 microM for 10 min), but not KCl (50 mM), exposure resulted in a significant inhibition of CaM kinase II activity. The inhibition of CaM kinase II activity was observed immediately following excitotoxic glutamate exposure and present at every time point measured. Glutamate-induced inhibition of kinase activity and delayed neuronal cell death was dependent upon both the activation of the NMDA glutamate receptor subtype and the presence of extracellular calcium. The relationship between inhibition of CaM kinase II activity and loss of intracellular calcium regulation was also examined. Experimental conditions which resulted in significant neuronal cell death and inhibition of CaM kinase II activity also resulted in a long-term loss of intracellular calcium regulation. Thus, inhibition of CaM kinase II activity occurred under experimental conditions which resulted in loss of neuronal viability and loss of neuronal calcium regulation. Since the glutamate-induced inhibition of CaM kinase II activity preceded neuronal cell death, the data support the hypothesis that inhibition of CaM kinase II activity may play a significant role in excitotoxicity-dependent, delayed neuronal cell death.

Topics: 6-Cyano-7-nitroquinoxaline-2,3-dione; Animals; Animals, Newborn; Blotting, Western; Calcium; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases; Cell Aggregation; Cells, Cultured; Dizocilpine Maleate; Glutamic Acid; Glycine; Hippocampus; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Kinetics; Microscopy, Fluorescence; N-Methylaspartate; Neurons; Neurotoxins; Peptides; Phosphorylation; Potassium Chloride; Quisqualic Acid; Rats; Receptors, N-Methyl-D-Aspartate