Fig. 2. (A ) γ-Aminobutyric acid (GABA)-induced Cl⁻currents recorded from a human embryonic kidney 293 cell expressing the wild-type GABA^Aα1β2γ2s receptor (top ) or α2β3γ2s receptor (bottom ). Cells were voltage clamped at −60 mV and GABA was applied with the rapid solution changer. Bars  over current traces  show the duration of rapid GABA application with the concentration (μm) of applied GABA. (B ) Concentration-response curves for the wild-type GABA^Aα1β2γ2s receptor (open circles ) and mutant receptors, α1(S270W) β2γ2s (filled circles ) and β2(N265W) β2γ2s (filled triangles ). GABA currents were expressed as a fraction of the maximal GABA response and these normalized data were fitted by a Hill equation. Data points  are shown as the means of at least six cells and error bars  indicate SEM. In some cases, the error bars are smaller than the symbols. (C ) Concentration-response curves were also constructed in the wild-type GABA^Aα2β3γ2s receptor (open circles ) and receptor mutated at α2(S270I) (filled circles ). Data are constructed from at least eight dose-response curves.