Calcium permeability of the N-methyl-D-aspartate receptor channel in hippocampal neurons in culture.

We have developed a quantitative description for calcium permeability of the N-methyl-D-aspartate receptor channel to permit predictions of the reversal potential and calcium influx at different voltages for different extracellular calcium concentrations. Increasing the external calcium concentration markedly shifted the reversal potential to positive values and simultaneously decreased the single-channel conductance at potentials negative to the reversal potential. Very simple quantitative descriptions of calcium permeation and channel block by calcium ions accurately characterize our data and permit the prediction of reversal potentials and magnitudes of calcium influx for a wide range of conditions.