3-Heteroaryl-2-pyridones:  Benzodiazepine Site Ligands with Functional Selectivity for α2/α3-Subtypes of Human GABAA Receptor-Ion Channels

A novel series of 3-heteroaryl-5,6-bis(aryl)-1-methyl-2-pyridones were developed with high affinity for the benzodiazepine (BZ) binding site of human γ-aminobutyric acid (GABAA) receptor ion channels, low binding selectivity for α2- and/or α3- over α1-containing GABAA receptor subtypes and high binding selectivity over α5 subtypes. High affinity appeared to be associated with a coplanar conformation of the pyridone and sulfur-containing 3-heteroaryl rings resulting from an attractive S...O intramolecular interaction. Functional selectivity (i.e., selective efficacy) for α2 and/or α3 GABAA receptor subtypes over α1 was observed in several of these compounds in electrophysiological assays. Furthermore, an α3 subtype selective inverse agonist was proconvulsant and anxiogenic in rodents while an α2/α3 subtype selective partial agonist was anticonvulsant and anxiolytic, supporting the hypothesis that subtype selective BZ site agonists may provide new anxiolytic therapies.