Transient Expression Shows Ligand Gating and Allosteric Potentiation of GABA A Receptor Subunits

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Abstract
Human γ-aminobutyric acid A (GABA A ) receptor subunits were expressed transiently in cultured mammalian cells. This expression system allows the simultaneous characterization of ligand-gated ion channels by electrophysiology and by pharmacology. Thus, coexpression of the α and β subunits of the GABA A receptor generated GABA-gated chloride channels and binding sites for GABA A receptor ligands. Channels consisting of only α or β subunits could also be detected. These homomeric channels formed with reduced efficiencies compared to the heteromeric receptors. Both of these homomeric GABA-responsive channels were potentiated by barbiturate, indicating that sites for both ligand-gating and allosteric potentiation are present on receptors assembled from either subunit.