DIFFERENTIAL LONG-LASTING POTENTIATION OF THE NMDA AND NON-NMDA SYNAPTIC CURRENTS INDUCED BY METABOTROPIC AND NMDA RECEPTOR COACTIVATION INCEREBELLAR GRANULE CELLS

Whole-cell patch-clamp recordings in rat cerebellar slices were used t o investigate the effect of metabotropic glutamate receptor activation on messy fibre-granule cell synaptic transmission. Transient applicat ion of 20 mu M 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid simulta neously with low-frequency NMDA receptor activation induced long-lasti ng non-decremental potentiation of both NMDA and non-NMDA receptor-med iated synaptic transmission. Potentiation could be prevented by applic ation of the metabotropic glutamate receptor antagonist (+)-O-methyl-4 -carboxyphenyl-glycine at 500 mu M. Characteristically, NMDA potentiat ion was two to three times as large as non-NMDA current potentiation, occurred only in a slow subcomponent, and was voltage-independent. Thi s result demonstrates a pivotal role of NMDA receptors in the metabotr opic potentiation of transmission, which may be important in regulatin g cerebellar information processing.