Influence of different point mutations on the concentration dependence of GABA. Wild type or mutant β2γ2 GABAA receptors were expressed in Xenopus oocytes and exposed to subsequently higher concentrations of GABA and the elicited current amplitude was determined. Individual curves for each subunit combination were first normalized to the fitted maximal current amplitude and subsequently averaged. Averaged concentration-response curve are shown. Data are expressed as mean ± S.E.M., n = 3–7 from two batches of oocytes.