Exposure of hippocampal slices to magnesium-free medium produces epileptiform activity and simultaneously decreases calcium and calmodulin-dependent protein kinase II activity.
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.
Churn
S B
SB
Department of Pharmacology and Toxicology, Medical College of Virginia, Richmond 23298.
Anderson
W W
WW
DeLorenzo
R J
RJ
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
D003470:Culture Media; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D008274:Magnesium