Fig. 2. γ-Aminobutyric acid (GABA) concentration-responses in the absence and presence of etomidate. Results for different pairs of concatenated GABA^Areceptor subunit assemblies are shown as pairs of panels: D^wtT^wt(A  and E ), D^αM236WT^αM236W(B  and F ), D^αM236WT^wt(C  and G ), and D^wtT^αM236W(D  and H ). A–D  display examples of current traces recorded from oocytes using two-electrode voltage clamp. Within each panel, control GABA responses are shown in the top row of traces, and responses in the presence of 3.2 μM etomidate are shown in the bottom row of traces. Each row of traces was recorded from a single oocyte. Labels above the traces show GABA concentrations (μM) used to elicit currents. E–H  display GABA concentration-responses in the absence or presence of etomidate, normalized to the maximal GABA response. Each symbol  represents mean ± SD of at least four independent measurements from different oocytes, but full concentration-response data sets were not obtained in every oocyte. Solid symbols  represent control GABA responses and open symbols represent GABA responses in the presence of 3.2 μM etomidate. Lines  through data represent fits to logistic functions (eq. 1, see Materials and Methods). Fitted parameters for each type of receptor are reported in table 1. Marked in panels E–H  are D^wtT^wtcontrol (E , solid squares ); D^wtT^wt+ etomidate (E , open squares ); D^αM236WT^αM236Wcontrol (F , solid triangles ); D^αM236WT^αM236W+ etomidate (F , open triangles ); D^αM236WT^wtcontrol (G , solid circles ); D^αM236WT^wt+ etomidate (G , open circles ); D^wtT^αM236Wcontrol (H , solid diamonds ); D^wtT^αM236W+ etomidate (H , open diamonds ). GABA = γ-aminobutyric acid.