Protein kinase C regulates ionic conductance in hippocampal pyramidal neurons: electrophysiological effects of phorbol esters.

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Abstract
The vertebrate CNS contains very high concentrations of protein kinase C, a Ca and phospholipid-stimulated phosphorylating enzyme. Phorbol esters, compounds with inflammatory and tumor-promoting properties, bind to and activate this enzyme. To clarify the role of protein kinase C in neuronal function, phorbol ester receptors were localized in the rat hippocampus by autoradiography and the electrophysiological effects of phorbol esters on hippocampal pyramidal neurons were examined in vitro. Phorbol esters blocked a Ca-dependent K conductance. Phorbol esters blocked the late hyperpolarization elicited by synaptic stimulation even though other synaptic potentials were not affected. The potencies of several phorbol esters in exerting these actions paralleled their affinities for protein kinase C, suggesting that protein kinase C regulates membrane ionic conductance.