(A) Etomidate and carboetomidate concentration–response relationships for α₁(L264T)β₃γ₂ γ-aminobutyric acid type A (GABA_A) receptor direct activation. Each data point is the mean value (± SD) obtained from four to six different oocytes. Data for etomidate was taken from Ref. 13. The curves are fits of the two data sets to a Hill equation yielding half-maximal direct activating concentrations of 1.83 ± 0.28 and 13.8 ± 0.9 µM for etomidate and carboetomidate, respectively (P < 0.0001). (B) Racemeic and S-pentafluoroetomidate concentration–response relationships for α₁(L264T)β₃γ₂ GABA_A receptor direct activation. Each data point is the mean value (± SD) obtained from six different oocytes. The curves are fits of the two data sets to a Hill equation yielding half-maximal direct activating concentrations of 7.6 ± 0.6 and 166 ± 25 µM, respectively (P < 0.0001). In each panel, the chemical structures are shown as insets with the differences between analogs highlighted in red.