GABA (γ -aminobutyric acid) is the principal inhibitory neurotransmitter in the mammalian brain. Its fast inhibitory actions are mediated by GABAA receptors representing ligand-operated chloride channels. GABAA receptors consist of 5 subunits generally belonging to different subunit classes (Macdonald and Olsen, 1994). Molecular cloning of complementary DNA encoding GABAA receptors in humans identified 8 different subunit classes with at least 20 different subunits (six α, four β, three γ, one δ, one e, one π, one θ, three ρ; Barnard et al., 1998). Each of these subunits exhibits a specific regional, cellular, and subcellular distribution in the brain (Wisden et al., 1992; Fritschy and Mohler, 1995; Sperk et al., 1997) that is partially overlapping with that of other subunits, indicating formation of a large number of different GABAA receptor subtypes with distinct subunit composition (For review, see Sieghart and Sperk, 2002). GABAA receptors are the site of action of several antiepileptic drugs (Olsen and Avoli, 1997), and depending on their subunit composition, exhibit distinct pharmacological and electrophysiological properties (Sieghart and Sperk, 2002). Most GABAA receptors consist of two α-, two β-, and one γ - (mostly γ 2) or one δ-subunit. Actions of GABA are primarily mediated by a β-subunits within the receptor, those of benzodiazepines by an α-subunit, involving however also interactions with the other subunits (β and γ 2). Reduced GABA-ergic function resulting from reduced GABA synthesis (Freichel et al., 2006), reduced reuptake (Chiu et al., 2005), mutations of GABAA receptor subunits (e.g., subunits α1, β3, or γ 2; DeLorey et al., 1998; Baulac et al., 2001; Cossette et al., 2002), or altered function of chloride transporters building the chloride ion gradient (Haug et al., 2003) cause epilepsies in humans and experimental animals. On the other hand, it has been suggested that status epilepticus or subsequent epileptogenesis may induce altered expression of individual GABAA receptor subunits and modified assembly of GABAA receptors. Hypthetically, this could result in altered GABA ergic transmission possibly contributing to increased seizure susceptibility or reduced sensitivity of drugs acting by enhancing GABAergic transmission.