Inhibition of propofol-mediated potentiation of α₁β₃γ_2L γ-aminobutyric acid type A (GABA_A) receptor currents by naphthalene–etomidate. (A) Propofol concentration-response curves for potentiation of γ-aminobutyric acid (GABA)-evoked currents in the absence and presence of 300 μM naphthalene–etomidate. The curves are fits of the data sets to equation 1. The propofol concentration that half-maximally potentiated GABA-evoked currents (EC₅₀) was 6.0 μM (95% CI, 4.4 to 8.0 μM) in the absence of naphthalene–etomidate and 36 μM (95% CI, 17 to 78 μM) in the presence of 300 μM etomidate. The respective slopes were 1.5 (95% CI, 0.97 to 2.1) and 1.0 (95% CI, 0.54 to 1.5 μM). In the absence and presence of 300 μM naphthalene–etomidate, the maximal responses at high propofol concentrations were essentially identical with values of 88% (95% CI, 81 to 96%) and 87% (95% CI, 66 to 107%), respectively. (B) Naphthalene–etomidate concentration-response curves for inhibition of GABA-evoked currents potentiated by 10 μM propofol. The curves are fits of the data sets to equation 2. The naphthalene–etomidate concentration that half-maximally inhibited potentiated currents (IC₅₀) was 62 μM (95% CI, 38 to 103 μM) with a minimum value of 24% (95% CI, 17 to 31%) and a slope of −3.9 (95% CI, −9.7 to −0.4). In both panels, each data point is the mean ± SD of four oocyte experiments.