ACTIVATION OF METABOTROPIC GLUTAMATE RECEPTORS IS NECESSARY FOR LONG-TERM POTENTIATION IN THE DENTATE GYRUS AND FOR SPATIAL-LEARNING

We have examined the effects of the metabotropic glutamate receptor an tagonist (RS)-a-methyl-4-carboxyphenylglycine (MCPG) on performance in the water maze, and on LTP in the dentate gyrus, MCPG (5 mM) reversib ly blocked the induction of LTP in the perforant path-granule cell pro jection when perfused into the dentate gyrus of the anaesthetized rat. When injected bilaterally into the lateral ventricles, MCPG (20 mM) d isrupted the performance of rats in a spatial learning version of the water maze task. In a terminal experiment, when tetanic stimulation wa s given to the perforant path, LTP was found to be significantly reduc ed in MCPG-injected rats compared to control rats injected with vehicl e. These experiments indicate that activation of MCPG-sensitive metabo tropic glutamate receptors is necessary both for the full expression o f LTP and spatial learning, and supply further evidence for the hypoth esis that LTP provides synaptic mechanism for certain forms of learnin g.