METABOTROPIC GLUTAMATE RECEPTOR-INDUCED HOMOSYNAPTIC LONG-TERM DEPRESSION AND DEPOTENTIATION IN THE DENTATE GYRUS OF THE RAT HIPPOCAMPUS IN-VITRO

We have investigated the role of metabotropic glutamate receptors (mGl uR) in the induction of homosynaptic long-term depression (LTD) and de potentiation (DP) in the dentate gyrus of the adult rat. Perfusion of the mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (1 S,3R-ACPD) for a prolonged period (20 min) induced long-term depressio n (LTD) of field excitatory postsynaptic field potentials (epsps) from the baseline level and also depotentiation (DP) from the long-term po tentiated level. Both the ACPD-and the low frequency stimulation (LFS) -induced LTD and DP were inhibited in the presence of the mGluR antago nist (+)-alpha-methyl-4-carboxyphenylglycine (MCPG), demonstrating the necessity for the activation of metabotropic glutamate receptors in t he induction of LTD/DP. The LFS and ACPD-induced LTD were independent of the activation of N-methyl-D-aspartate (NMDA) receptors, as they we re not blocked by the NMDA receptor antagonist D-2-amino-5-phophonopen tanoate (AP5).