Activation of group-II metabotropic glutamate receptors blocks induction of long-term potentiation and depotentiation in area CA1 of the rat in vivo.

The metabotropic glutamate receptor group-II agonist (1S,3S)-1-aminocyclopentane-1,3-dicarboxylic acid (1S,3S-ACPD; 5 microliters/10 mM, i.c.v.) prevented the induction of long-term potentiation and depotentiation in the CA1 area of the hippocampus in urethane-anaesthetised rats. These effects were prevented by the group-II metabotropic glutamate receptor antagonists alpha-methyl-(2S,3S,4S)-alpha-(carboxycyclopropyl)glycine (MCCG; 5 microliters/100 mM) and (RS)-alpha-methyl-4-tetrazolylphenylglycine (MTPG; 5 microliters/500 mM). The group-I antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA; 5 microliters/200 mM) or the group-III antagonist alpha-methyl-L-2-amino-4-phosphonobutyrate (MAP4; 5 microliters/100 mM) did not affect the block of the induction of long-term potentiation by 1S,3S-ACPD. It is concluded that activation of group-II metabotropic glutamate receptors can block both high-frequency stimulation-induced long term potentiation and low-frequency stimulation-induced depotentiation in the CA1 area in vivo.