cinolazepam (Sieghart, 1989) or non-benzodiazepines such as zolpidem, Cl218872, abecarnil, zaleplon and indiplon (for review see Möhler, 2006), have been developed that exhibit a preferential selectivity for α1βγ2 receptors. Most of these compounds exhibit sedative and hypnotic properties. Other compounds, such as SL651498 (Griebel et al., 2003) or TPA023 (Atack et al., 2006) seem to exhibit a certain selectivity for α2βγ2 and α3βγ2 receptors, whereas L-838,417 (McKernan et al., 2000) exhibits a selectivity for α2βγ2, α3βγ2 and α5βγ2 receptors. All these compounds exhibit anxiolytic properties. One of the few non-sedative, anxiolytic compounds that is not α2 subunit-selective is ocinaplon (Basile et al., 2004; Atack, 2005). The compound L-655 708 is a partial inverse agonist with preference for α5βγ2 receptors and exhibits memory-enhancing properties (Sternfeld et al., 2004;Chambers et al., 2004), α3IA is a weak inverse agonist at α3βγ2 receptors that has anxiogenic actions (Atack et al., 2005). The overall selectivity of most of these drugs, however, is not yet sufficient for a selective activation of a single GABAA receptor subtype, allowing the unequivocal identification of these receptor subtypes and their function in the brain.
