The recent review on GABAA-R (Olsen & Sieghart, 2008) provides a compendium of criteria for inclusion of candidate subtypes on a list of native receptors, and the resulting receptor list. Whether all these receptor subtypes as well as those still to be identified are biologically relevant currently cannot be answered. A specific subunit composition could allow, for example, specific targeting to a certain subcellular localization, specific regulation by protein kinases and phosphatases, or interaction with other associated proteins or other receptors. Thus we will need to continue to develop careful approaches for defining which receptor subtypes are native, especially the lower abundance subtypes. Three categories of subtypes are designated: Identified; Existence with High Probability; and Tentative. A ‘working list’ of receptor subtypes totaling 26 is provided in Olsen & Sieghart (2008), reproduced here (Table 1). The 19 subunit genes also are presented in Olsen & Sieghart (2008), and the subunit list for all LGIC genes is included in the introductory chapter for this volume (Collingridge et al., 2008).
