title: Exposure of hippocampal slices to magnesium-free medium produces epileptiform activity and simultaneously decreases calcium and calmodulin-dependent protein kinase II activity.
abstract: The effect of magnesium-free medium on electrical and CaM kinase II activity in the rat hippocampal slice was examined. Experimental slices were incubated in 2 mM Mg, then exposed to magnesium-free medium for 1 h. Control slices were concurrently run in 2 mM Mg. Slices were then frozen and CaM kinase II activity was measured in homogenates. Exposure of hippocampal slices to magnesium-free medium resulted in spontaneous epileptiform activity and a concurrent 38 +/- 5.47% decrease in CaM kinase II activity (range 38.8-75.4% of control; n = 7, P less than 0.001, paired Student's t test). The decrease in CaM kinase II activity was not reversible by treatment with protein phosphatases 1 and 2A (58.8 +/- 4.77% of control activity; range 28.6-69.7, P less than 0.01, paired Student's t-test), indicating that the decrease in CaM kinase II activity cannot be accounted for exclusively by autophosphorylation. The results demonstrate that magnesium-free medium treatment can induce spontaneous epileptiform activity and simultaneous changes in CaM kinase II activity.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Virginia, Richmond 23298.
authors.forename: S B
authors.initials: SB
authors.lastname: Churn
authors.forename: W W
authors.initials: WW
authors.lastname: Anderson
authors.forename: R J
authors.initials: RJ
authors.lastname: DeLorenzo
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D003470:Culture Media; D004558:Electric Stimulation / Q000379:methods; D004827:Epilepsy / Q000201:enzymology / Q000503:physiopathology*; D005260:Female; D006624:Hippocampus / Q000201:enzymology / Q000502:physiology*; D008274:Magnesium / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D003470:Culture Media; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D008274:Magnesium