Changes in the reversal potential of NMDG⁺ currents with the addition of low concentrations of K⁺_o. (A) The pulses used for the experiments shown in B–D. A depolarizing step from −100 to +60 mV was followed by repolarization to different potentials ranging from −50 to +20, +40, and +50 mV in B–D, respectively. The pulses were applied at 0.1 Hz. (B–D) Currents recorded in the presence of symmetrical 140 mM NMDG⁺_i/o plus the concentration of K⁺_o indicated in the figure. The internal solutions were Mg²⁺ free in all experiments. (E) Peak tail current–voltage curves showing the shift in reversal potential produced by the addition of 0.3 or 1 mM of extracellular K⁺. Data from B–D: n = 4.