We examined the effect of acute ethanol exposure on the GABA response in oocytes injected with 1:1:1, 2:2:1 or 6:2:1 ratios of α2, β2, and γ3 subunit mRNAs (Figure 3). Each oocyte was challenged with 1 μM GABA while monitoring current size under voltage-clamp conditions before and after ethanol pretreatment. This GABA concentration (1 μM) approximates the EC20 for GABA as determined above (see Figure 2B and 2C) and should allow detection of either potentiation or inhibition of GABA response by ethanol. GABA currents were normalized to control currents before ethanol treatment for each oocyte. Ethanol significantly potentiated the amplitudes of GABA-induced currents by 93% in oocytes injected with a 1:1:1 ratio of α2, β2, and γ3 subunit mRNAs (p < 0.01, n = 16). Ethanol also potentiated the amplitudes of GABA-induced currents by 24% in oocytes injected with a 2:2:1 ratio of α2, β2, and γ3 subunit mRNAs (p < 0.01, n = 15). In contrast, ethanol inhibited the amplitudes of GABA-induced currents by 19% in oocytes injected with a 6:2:1 ratio of α2, β2, and γ3 subunit mRNAs (p < 0.01, n = 19).
