The glutamate- and glycine-induced reduction of [3H]MK-801 binding in the presence of Mg2+ is reversed at low pH.

At normal pH, glutamate and glycine are known to inhibit [3H]MK-801 binding in the presence of Mg2+. We found, however, that at pH 5.4 glutamate and glycine enhance [3H]MK-801 binding in rat cerebrocortical membranes. Furthermore, H+, similarly to Mg2+, inhibited basal [3H]MK-801 binding. These results indicate that H+ competes with binding sites for Mg2+ and [3H]MK-801, and may be correlated to the depression in neuronal activity observed during acidosis.