Fig. 5. Allosteric coagonist models for γ-aminobutyric acid (GABA) and etomidate-dependent receptor activation. Estimated open probabilities were calculated from mean normalized concentration-response data ( figs. 1 and 2,) using equation 2. Solid symbols represent control GABA concentration-responses, open symbols represent GABA responses in the presence of 3.2 μm etomidate, and cross-hatched symbols represent etomidate direct activation responses. Combined data for each channel type were fitted with equation 3(Methods), and results are plotted as solid lines in the panels. Fitted parameters are reported in table 2. ( A ) Wild-type α1β2γ2L ( square symbols ); ( B ) α1β2(N265S)γ2L ( circles ); ( C ) α1β2(N265M)γ2L ( triangles ).