Diazepam inhibits calcium, calmodulin-dependent protein kinase in primary astrocyte cultures.
The effect of the anticonvulsants diazepam, phenytoin, and valproic acid on calcium, calmodulin-dependent protein phosphorylation in astrocytes was investigated. We found that diazepam inhibited calcium, calmodulin-stimulated phosphorylation in both supernatant and membrane fractions from primary cultures of rat astrocytes, whereas phenytoin and valproic acid (50-500 microM) had little to no effect. Phosphate incorporation in several protein bands, including the major substrates of 59 and 53 kDa, was inhibited by diazepam. A decrease in phosphate incorporation in these crude preparations was observed at 25 microM diazepam and 50% inhibition was attained at about 100 microM. Dibutyryl cyclic AMP-treated astrocytes were enriched in the 59 kDa phosphoprotein; this band was particularly sensitive to diazepam in these cells. These results indicate that diazepam is capable of inhibiting calcium, calmodulin-dependent protein kinase activity in astrocytes, thereby suggesting a possible site of diazepam action and a potential mechanism for a role of astrocytes in epileptogenesis.
Babcock-Atkinson
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Laboratory of Neuropathology, VA Medical Center, Miami, FL 33125.
Norenberg
L O
LO
Norenberg
M D
MD
Neary
J T
JT
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002478:Cells, Cultured; D003975:Diazepam / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
D000927:Anticonvulsants; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D003975:Diazepam; D002118:Calcium