Gamma-aminobutyric acid (GABA)-gated ion channels are widely distributed in the mammalian brain and are major mediators of inhibitory synaptic transmission. A typical GABA ion channel has a pentameric structure consisting of 5 protein subunits, often alpha, beta and gamma or delta, combining to form a central ion conducting pore across the cell membrane. In humans there are six genes that encode alpha subunits, three that encode beta, three that encode gamma, and an additional seven genes that encode other subunits whose function is less-well understood than the alpha, beta and gamma subunits. GABA ion channels open and close in response to secretion of GABA from presynaptic terminals. GABAA alpha2 channels are typically comprised of alpha2, beta3, and gamma2 subunits, and it is estimated that this GABA subtype represents 15-20% of all GABAA receptors located in the brain, with a synaptic localization. Much pharmaceutical research interest has focused on alpha2-selective compounds to treat anxiety disorders, because data from transgenic mice implicate alpha1-containing receptors as mediators of the sedative effects of diazepam. Diazepam-like compounds that are selective for alpha2- or alpha3-containing receptors show promise as non-sedating anxiolytics.