The direct effect of lithium and carbamazepine on protein kinase C in rat brain.

The effect of carbamazepine on protein kinase C, which is believed to phosphorylate a number of proteins, was compared with that of lithium in vitro. Lithium did not significantly inhibit the protein kinase C activity in the rat cerebral cortex in vitro, and 0.01 mM of carbamazepine had no inhibitory effect on the enzyme activity. However, inhibition did begin to appear at 1 mM. The Lineweaver-Burk plot of carbamazepine was similar to the competitive inhibition pattern. The data suggest that lithium and carbamazepine as mood stabilizers have the same effect on the manic state, but their mechanism reducing mania may differ in the cell signal transduction pathways.