Direct activation of α1β3γ2L GABAA receptor with the enantiomers of barbiturate 14. Currents were elicited with increasing amounts of drug. With the exception of not using GABA, all conditions were the same as in Figure 3. Upper and lower traces show current responses to the stated concentrations of R-(−)-14 and S-(+)-14. For R-(−)-14 (circles): EC50 = 13 ± 8 μM, nH = 1.1 ± 0.4, Imax = 26 ± 5% (4 oocytes). For S-(+)-14 (squares): EC50 = 61 ± 6 μM, nH = 1.9 ± 0.2, Imax = 3 ± 0.1 % (one oocyte due to amount of material required). For least squares analysis, currents were normalized to the maximal GABA response for each oocyte.