Fig. 9.

Allopregnanolone and ganaxolone potentiation of GABA responses of α1β3γ2 GABA_AR in HEK 293 cells. (A) Concentration-response curves for allopregnanolone and ganaxolone potentiation of FMP-Red Dye responses to 10 nM GABA. The graph plots mean ± S.D. fold increase in peak response in the presence the NAS compared with the response to 10 nM GABA alone. Each data point is the mean ± S.D. of measurements of 10 wells. The EC₅₀ values for allopregnanolone and ganaxolone are 1.7 nM [95% confidence interval (CI): 1–3.1 nM (n_H = 1.5)] and 20 nM [95% CI: 14–55 nM (n_H = 1.4)], respectively (P < 0.0001). Dose-response curves were plotted using nonlinear regression with a four-parameter logistic equation and independent F test was applied to determine the statistical differences for EC₅₀ values and slopes between allopregnanolone and ganaxolone in combination with 10 nM GABA in α1β3γ2 GABA_AR in HEK 293 cells. Inset shows representative traces with addition of GABA alone and GABA plus allopregnanolone at concentrations of 1 and 10 nM. (B) Concentration-response curves for allopregnanolone and ganaxolone potentiation of peak inward Cl⁻ current responses to 1 μM GABA (EC₁₀ value) in patch-clamp recordings. Each data point is the mean ± S.D. of measurements of 3–6 cells. The EC₅₀ values for allopregnanolone and ganaxolone are 71.3 nΜ [95% CI: 57.1–85.5 nM (n_H = 1.8)] and 114.8 nΜ [95% CI: 99.2–130.4 nM (n_H = 2.2)], respectively. Inset shows representative traces with application of GABA alone and GABA plus allopregnanolone at 100 and 175 nM.