EVIDENCE AGAINST A ROLE FOR METABOTROPIC GLUTAMATE RECEPTORS IN MOSSYFIBER LTP - THE USE OF MUTANT MICE AND PHARMACOLOGICAL ANTAGONISTS

We have used a number of approaches to address a possible role of meta botropic glutamate receptors (mGluRs) in messy fiber long-term potenti ation (LTP) in the hippocampus. We have used two types of mutant mice- one lacking the mGluR1 subtype of receptor and one lacking the gamma i soform of protein kinase C. In neither type of mouse did we find any a lteration in the magnitude of messy fiber LTP. We next examined whethe r mGluRs might modulate the magnitude and/or threshold for the inducti on of messy fiber LTP. In these experiments we used tetani that were e ither just subthreshold or just suprathreshold for generating LTP. The mGluR antagonist (+)-alpha-methyl-4-carboxyphenylglycine [(+)MCPG] di d not convert a subthreshold tetanus into a suprathreshold tetanus, no r did (+)MCPG have any effect on the small amount of LTP that was gene rated by a just suprathreshold tetanus. Based on our studies, we have been unable to identify a role for mGluRs in messy fiber LTP.