METABOTROPIC GLUTAMATE RECEPTORS TRIGGER POSTSYNAPTIC PROTEIN-SYNTHESIS

K+ depolarization or addition of glutamate to a synaptoneurosome prepa ration triggers a rapid increase in size of polyribosomal aggregates i solated by centrifugation of lysate through 1 M sucrose. The profile o f response to the glutamate analogues quisqualate, ibotenate, and 1-am inocyclopentane-1,3-dicarboxylate corresponds to that of metabotropic receptors. Glutamate stimulation is mimicked by the diacylglycerol ana logue 1-oleoyl-2-acetylglycerol and by the protein kinase C activator phorbol dibutyrate. The phospholipase blockers 2-nitro-4-carboxyphenyl -N,N-diphenylcarbamate and quinacrine reduce the late phase of the res ponse. The protein kinase C inhibitor calphostin C suppresses the resp onse to 1-aminocyclopentane-1,3-dicarboxylate. These data indicate tha t glutamatergic synapses upregulate postsynaptic protein synthesis via metabotropic glutamate receptors coupled to the phosphatidylinositol second-messenger system. This mechanism could underlie the reported in volvement of metabotropic glutamate receptors in long-term potentiatio n and other forms of neural plasticity.