Fig. 2. Enhanced Ca2+permeability and increased kainate potency in GluR2-deficient cortical pyramidal neurons. A–C, Representative kainate-evoked (100 μm) whole-cell currents and the I–Vrelationships for averaged steady-state currents in GluR2 mutant neurons recorded in low (1 mm, open symbols) and high (20 mm, filled symbols) extracellular Ca2+. Curves were fit by a fourth order polynomial equation from which interpolated reversal potentials were calculated.Erev(+/+), +1.1 ± 0.9 and +0.6 ± 1.1 mV;Erev(+/−), −0.4 ± 1.2 and −0.3 ± 1.0 mV;Erev(−/−), +4.5 ± 2.5 and +11.8 ± 2.3 mV, for low and high Ca2+, respectively. D, Representative kainate-evoked whole-cell currents and concentration–response relationships for peak kainate-evoked currents recorded in GluR2 mutant cortical pyramidal neurons. Concentration–response curves at 10, 30, 100, 300, 1000, and 3000 μm kainate were constructed and normalized to the maximal response in GluR2(+/+)(▪), GluR2(+/−) (■), and GluR2(−/−) (▵) neurons. The potencies of kainate (EC50) and Hill coefficients (nH) were determined by fitting the curves to the equation: I =Imax × 1/(1 + (EC50/[kainate])n), whereImax in the response at 3 mm kainate. GluR2(+/+)EC50, 142.252 ± 15.672 μm;nH, 1.330 ± 0.027 (n = 19). GluR2(+/−)EC50, 131.286 ± 26.692 μm;nH, 1.303 ± 0.062 (n = 11). GluR2(−/−)EC50, 56.511 ± 7.480 μm;nH, 1.159 ± 0.048 (n = 15). *Differences from GluR2(+/−) and GluR2(+/+), one-way ANOVA (F = 8.155; p = 0.001) with post hocBonferroni t tests; p < 0.05.E, Currents from D plotted without normalization to Imax.