A novel metabotropic glutamate receptor agonist: (2S,1'S,2'R,3'R)-2-(2-carboxy-3-methoxymethylcyclopropyl)glycine (cis-MCG-I).

A novel agonist for metabotropic glutamate receptors, (2S,1'S,2'R,3'R)-2-(2-carboxy-3-methoxymethylcyclopropyl)glycine (cis-MCG-I), effectively inhibited monosynaptic excitation in newborn rat spinal cords with EC50 of 3 microM without causing any depolarization. Furthermore, cis-MCG-I inhibited the forskolin-stimulated cyclic AMP formation in rat cultured cortical cells with IC50 of 1.5 microM. cis-MCG-I neither stimulated the phosphoinositide hydrolysis nor activated ionotropic glutamate receptors even in high concentrations. However, after a brief exposure of spinal cords to quisqualate, it caused depolarization in a dose-dependent manner. This compound would provide useful information for elucidating physiological functions of metabotropic glutamate receptors.