NPS Pharmaceuticals, Inc. (NPS) has synthesized a series of openchannel blo
ckers with varying potencies at the NMDA receptor. NPS 1506 (Fig. 1) is a m
oderate affinity antagonist that inhibits NMDA/glycine-induced increases in
cytosolic calcium in cultured rat cerebellar granule cells (IC50 = 476nM)
and displaces the binding of [H-3]MK-801 to rat cortical membranes (IC50 =
664nM).