High affinity, selective metabotropic glutamate receptor type 1 (mGlu1) antagonist. Binds an allosteric site of the rat mGlu1 receptor with a Ki of 4.8 nM. Inhibits mGlu1-mediated inositol phosphates production (IC50 = 8.6 nM in rat cerebellar granule cells). Neuroprotective in vivo.