An antagonist of the metabotropic glutamate receptor prevents LTP in the dentate gyrus of freely moving rats.

The effect of the competitive metabotropic glutamate receptor antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) on long-term potentiation (LTP) in the dentate gyrus was studied in freely moving rats. Intracerebroventricular infusion of MCPG (0.0208 mg) 30 min prior to tetanic stimulation reduced the duration of LTP of the population spike amplitude to 2-3 hr. MCPG itself was without effect on the basal responses evoked by test stimuli. These results provide the first evidence for the requirement of activation of metabotropic glutamate receptors for the induction and maintenance of LTP at perforant path/dentate gyrus synapses in freely moving animals.