An antagonist of NR1A/2B subunit-containing NMDA receptors (IC50 = 0.0053 µM); selective for NMDA receptors containing NR1A/2B subunits over NMDA receptors containing NR1A/2A and NR1A/2C subunits (IC50s = 35 and >100 µM, respectively); inhibits L-DOPA-induced contralateral rotations in a rat model of 6-OHDA-induced Parkinson's disease at 10 mg/kg; has been radiolabeled and used as an NR1A/2B-selective PET radiotracer