Ca2+ permeability of coexpressed mutant NMDAR subunits. Overview of the Ca2+ permeabilities of diheteromers featuring N and N+1 site mutant NMDAR subunits. To the right, PCa2+/Pmono ratios for the investigated combinations are given; the graphs represent those values on a relative scale. For NR1/NR2 combinations, measurements of Ca2+ permeability were performed after the application of 100 μM glutamate (Glu) and 10 μM glycine (Gly). NR1/NR3 diheteromers were activated by glycine alone. n = 5-9.