170301-14-1Relevant articles and documents
Studies in the search for α5 subtype selective agonists for GABA(A)/BzR sites
Yu, Shu,Ma, Chunrong,He, Xiaohui,McKernan, Ruth,Cook, James M.
, p. 71 - 88 (2007/10/03)
In the search for α5 selective ligands, several series of diazepam analogs with individual and/or simultaneous modifications at positions-2, -5 and -7 were prepared and their in vitro affinities determined on recombinant receptors. These ligands were deliberately designed to test the effects of interaction at H1, H2, L2 and L3 of the pharmacophore/receptor model on ligand binding affinities and selectivities at different GABA(A)/BzR subtypes. In agreement with previous reports, none of these 1,4- benzodiazepines bound to the α4β3γ2 and α6β3γ2 receptor isoforms, two diazepam-insensitive(DI) GABA(A) receptor subtypes which appear to be devoid of lipophilic pocket L3. The presence of a 2'-fluorophenyl or 2'-nitrophenyl group at the C(5) position enhanced ligand affinity for the receptors but favored α1β3γ2 subtypes over α5β3γ2 subtypes. Replacement of the 2'- fluorophenyl or 2'-nitrophenyl group with a phenyl, 2'-thienyl or 2'-furyl moiety at the same position resulted in lower affinities of the ligands at all GABA(A) subtypes. Most importantly, when the carbonyl groups at position- 2 were replaced by methylene moieties (21 and 23), the affinities for all subtypes diminished. These results strongly suggest that the hydrogen bonding interaction of the ligand at H1 (as well as H2) with the receptor protein is important for high affinity at all DS sites. This implies that H1 is very similar in all receptor isoforms and may not be a descriptor which will readily lend itself to pharmacological receptor subtype selectivity.
