Estrogen and SERMs rapidly attenuate the GABA_B response. A-F, Representative traces of the GABA_B responses before and after steroid treatment. Experiments were conducted as described in Figure 1. G, The chemical structures of E₂ and the SERMs. H, Bar graphs summarizing the effects of E₂ and SERMs on the baclofen response. E₂ (100 nm) attenuated the GABA_B receptor-mediated outward current by 41%. The inhibitory effects of E₂ on the baclofen response were blocked by the estrogen receptor antagonist ICI 182,780 (1 μm). E₂-BSA (100 nm), 4-OH tamoxifen (1 μm), raloxifene (1 μm), GW-5638 (1 μm), and STX (10 nm) also inhibited the baclofen response; however, 17α-E₂ (1 μm) had no effect. Error bars represent the mean ± SEM of 4-11 cells tested per group. ^*p < 0.05, ^**p < 0.01, and ^***p < 0.005, versus vehicle control group.