Hemin interacts with the BZ site of the GABA_A-R. (A) Hemin (2 and 10 μM) enhances submaximal GABA currents in one HEK 293 cell expressing α₁β₂γ_2s GABA_A-R. (B) Potentiation of GABA responses by hemin (2 and 10 μM) in one recombinant α₁β₂γ_2s HEK 293 cell is blocked by coapplication of flumazenil (4 μM). Scale bars, 1 nA and 4 s. (C) Dose dependence of hemin potentiation in α₁β₂γ_2s GABA_A-R. Points (□) are plotted as means ± SEM. Where not shown, errors were smaller than the size of the symbols. (D) Enhancement of the GABA response by hemin in recombinant α₁β₂γ_2s, α₁β₂ (*P < .01), and α₁His101Argβ₂γ_2s (*P < .01) receptors.