Metabotropic glutamate receptor antagonist, (R,S)-alpha-methyl-4-carboxyphenyglycine, blocks two distinct forms of long-term potentiation in area CA1 of rat hippocampus.

The necessity of metabotropic glutamate receptors (mGluRs) in the induction of long-term potentiation (LTP) has recently been questioned. We examined the effect of (R,S)-alpha-methyl-4-caboxyphenylglycine (MCPG), a selective mGluR antagonist, on two independent forms of LTP. One form induced by a 25 Hz/1 s tetanus is solely N-methyl-D-aspartate (NMDA) receptor-dependent. The other form induced by four 200 Hz/0.5 s bursts in the presence of APV is NMDA receptor-independent. In both paradigms the presence of MCPG prevented the induction of LTP by afferent activation.