GABAA receptors are heteromeric protein complexes consisting of several homologous membrane-spanning glycoprotein subunits. Molecular cloning has revealed multiple GABAA receptor subunits that can be divided by homology into subunit classes with several members: α(1–6), β(1–3), γ(1–3), δ, ε, θ, π, and ρ(1–3) (Olsen and Sieghart 2008; Sieghart and Sperk 2002). The large number of GABAA receptor subunits generates the potential for various subunit compositions that may account for variable sensitivity to modulatory drugs such as benzodiazepines, barbiturates, neuroactive steroids, and possibly ethanol and general anesthetics. The GABAA receptor α1 subunit is the most abundant α subunit in adult brain, highly expressed throughout most brain regions and is a component of ~50% of all GABAA receptors (Kralic et al. 2002a). The analysis of subunit composition by co-immunoprecipitation studies has demonstrated that 98% of α1 subunit-containing receptors are assembled with a γ or δ subunit (Sieghart and Sperk 2002). In contrast, a significant fraction of α4 subunit-containing receptors are comprised of α4 and β subunits only (Bencsits et al. 1999). GABAA receptors also associate with various other proteins that anchor the receptor,
