Figure 4. Protons alter sensitivities to LBD ligands and act through a novel site.

(a) Glycine-dose dependency of I_pk, at two pH values. (b) Glycine-elicited currents recorded in the continuous presence (50 μM, grey) or absence (0 μM, black or red) of external Zn²⁺ at two pH values, and zinc-dose dependency of I_pk change relative to 0 Zn²⁺ (I_CTR), at two pH values. (c) Glycine-elicited currents recorded with 1.8 mM external Ca²⁺ at several holding potentials, and the voltage dependence of I_pk relative to +80 mV (I₈₀) at two pH values. (d) Glycine-elicited currents from cells expressing GluN1-4a^F484A and GluN3A (GluN1-4a^F/A) at two pH values and summary of changes in I_pk. Values are means ± SEM; sample size is in bars; n/s, P > 0.05.