Intrahippocampal infusions of a metabotropic glutamate receptor antagonistblock the memory of context-specific but not tone-specific conditioned fear

The role of metabotropic glutamate receptors (mGluRs) in the acquisition of learning and memory using fear conditioning as a behavioral model was exam ined. The mGluR antagonist (R, S)-alpha-methyl-4-carboxyphenylglycine (MCPG ) was infused into the hippocampus 30 min before fear conditioning, and fre ezing was measured during both acquisition and retention tests. The results show that pretraining antagonism of MCPG-sensitive mGluRs in the hippocamp us impaired context-specific memory for an aversive event during testing. T he memory for tone-specific fear, however, remained intact despite pretrain ing infusion of MCPG. Treating rats with MCPG did not affect context- or to ne-specific fear during acquisition. Results suggest that mGluR activation may play an important role in hippocampally mediated memory consolidation.