Dominant effect of the K289M but not the R43Q mutation on synaptic GABA currents. A, Continuous records and scaled averages (dotted gray line) of ∼100 GABA_AR-mediated, miniature IPSCs recorded from transfected and untransfected hippocampal neurons. Averaged mIPSC decay was fit by a single exponential (plain line). B, Averaged data from 9 to 14 records from transfected and untransfected cells shows no differences in mean mIPSC amplitude, 10–90% time-to-peak, or frequency. However, mIPSCs decay faster in neurons expressing the K289M mutant than in untransfected neurons or neurons expressing wild-type GABRG2. C, Scaled, averaged mIPSCs recorded in the presence of 1 μm diazepam show increased decay time constant. D, Averaged data of diazepam-induced increase in mIPSC decay time constant (τ_off) in untransfected neurons, as well as neurons transfected with WT or mutant recombinant GABRG2, showing no difference between conditions. Calibration: 50 pA, 500 ms (continuous records); 20 ms (scaled averages). *p < 0.002.