Fig. 7. The α1(L264T) gating mutation used to interpret etomidate interactions with γ-aminobutyric acid receptor type A (GABA^A) receptors containing β1 or β2 subunits.  Panel A depicts GABA concentration-response data (mean ± SD) for oocytes expressing α1β1γ2L (  solid diamonds ) and α1(L264T)β1γ2L receptors (  open diamonds ). Lines represent fits to logistic functions: α1β1γ2L GABA EC⁵⁰= 190 ± 32 μm, Hill slope = 0.61 ± 0.064; α1(L264T)β1γ2L GABA EC⁵⁰= 3.8 ± 0.43 μm, Hill slope = 0.55 ± 0.073. (  B ) Estimated P^openvalues (mean ± SD) from etomidate concentration-response studies of both α1(L264T)β1γ2L (  crossed diamonds ) and α1(L264T)β2γ2L (  solid triangles ).  Lines through α1(L264T)β1γ2L points represent a nonlinear least squares fit to equation 3with [GABA]= 0: L⁰= 9.1 ± 0.84, K^E= 58 ± 6.4 μm, d = 0.26 ± 0.038. The  line through α1(L264T)β2γ2L data are equation 3with L⁰= 8 and other values set at those derived for α1β2γ2L receptors(K^E= 40 μm, d = 0.0076).