GluN2B-containing receptors show a reduced activation efficiency. (A and B) Currents from a patch containing a single human GluN1/GluN2B receptor. External solution is our standard at pH 7.4 with an energy-based internal (see Table 2). (C) Dwell time histogram of the latency to first opening for GluN1/GluN2B channels. The histogram was best fit by two exponentials (dashed lines). (D) Mean (±SEM) efficiency (η) of activation for various constructs, either rat (r) or human (h) N1/N2A (rN1/rN2A, hN1/hN2A) or human N1/N2B (hN1/hN2B). ****P < 0.0001, one-way ANOVA (P < 0.0001) with a post-hoc Tukey’s test: rN2A versus hN2A, P = 0.37; rN2A versus hN2B, P < 0.0001; hN2A versus hN2B, P < 0.0001. (E) Average delay (mean ± SEM) for various constructs. Note log scale. ****P < 0.0001, one-way ANOVA (P < 0.0001) with a post-hoc Tukey’s test: rN2A versus hN2A, P = 0.93; rN2A versus hN2B, P < 0.0001; hN2A versus hN2B, P < 0.0001.