Differential effects of F6 on heterodimeric α5β3 GABAA receptors. A. Responses to a two-second-long application of 1 mM GABA (top) and of 1 μM GABA (bottom). Middle traces were obtained during co-application of GABA and 16 μM F6. B. Concentration-response relationships for α5β3 GABAA receptors in the absence (circles, EC50 = 3.3 μM, slope = 1.48, n = 3–9) and presence (squares, EC50 = 1.83 μM, slope = 0.36, n = 4–6) of F6 (mean ± S.E.M).