Possible Role of Calcium‐Dependent Protein Phosphorylation in Mediating Neurotransmitter Release and Anticonvulsant Action

Abstract
Ca and phenytoin have antagonistic actions on net level of endogenous phosphorylation of specific rat brain proteins. These specific phosphoproteins apparently were present in synaptosome preparations, and evidence is presented for localization of these phosphoproteins within the presynaptic nerve terminal. The antagonistic actions of Ca and phenytoin on phosphorylation of synaptosome proteins may be the underlying molecular mechanism mediating opposing actions of these agents on release of neurotransmitter from the presynaptic nerve terminal.