Because chronic ethanol exposure affects GABA responses, we determined the effect of prolonged ethanol exposure on GABAA receptors composed of different ratios of subunits. For chronic treatment studies, half of the oocytes from each injection group were incubated in Oocyte Ringer containing ethanol for 16 hours immediately prior to voltage-clamp recording, while the control cells were incubated in Oocyte Ringer alone. Ethanol (44 or 100 mM as indicated) did not alter pH but slightly decreased osmolarity of the Oocyte Ringer solution. Resting membrane potentials and leakage current under initial voltage clamp conditions did not differ between the ethanol-treated groups and controls (data not shown) which suggests that the overall health of the oocytes is similar in controls and ethanol-treated groups. As shown in Figure 4A, chronic ethanol (44 mM) had no significant effect on GABA currents (1.0 ± 0.07, n = 20 vs. 0.85 ± 0.07, n = 18; p = 0.16) in oocytes injected with the presumed native 2:2:1 ratio of α2β2γ3 subunits. Likewise, chronic ethanol (44 mM) did not significantly change, although a trend is apparent, GABA currents
