Affinity of 3-acyl substituted 4-quinolones at the benzodiazepine site of GABA A receptors

24 3-acyl-4-quinolones with various substituents in position 6 were synthesized and assayed for affinity at the benzodiazepine site of GABA A receptors. The finding that alkyl 1,4-dihydro-4-oxoquinoline-3-carboxylate and N-alkyl-1,4-dihydro-4-oxoquinoline-3-carboxamide derivatives may be high-affinity ligands at the benzodiazepine binding site of the GABA A receptor, prompted a study of 3-acyl-1,4-dihydro-4-oxoquinoline (3-acyl-4-quinolones). In general, the affinity of the 3-acyl derivatives was found to be comparable with the 3-carboxylate and the 3-carboxamide derivatives, and certain substituents (e.g., benzyl) in position 6 were again shown to be important. As it is believed that the benzodiazepine binding site is situated between an α- and a γ-subunit in the GABA A receptor, selected compounds were tested on the α 1β 2γ 2s, α 2β 2γ 2s and α 3β 2γ 2s GABA A receptor subtypes. The 3-acyl-4-quinolones display various degrees of selectivity for α 1- versus α 2- and α 3-containing receptors, and high-affinity ligands essentially selective for α 1 over α 3 were developed.