Discovery of a new class of orthosteric antagonists with nanomolar potency at extrasynaptic GABA_A receptors.

ABSTRACT: Brain GABA_? receptors are ionotropic receptors belonging to the class of Cys-loop receptors and are important drug targets for the treatment of anxiety and sleep disorders. By screening a compound library (2,112 compounds) at recombinant human ?₄?₁? GABA_? receptors heterologously expressed in a HEK cell line, we identified a scaffold of spirocyclic compounds with nanomolar antagonist activity at GABA_? receptors. The initial screening hit 2027 (IC₅₀ of 1.03 ?M) was used for analogue search resulting in 018 (IC₅₀ of 0.088 ?M). 018 was most potent at ?_3,4,5-subunit containing receptors, thus showing preference for forebrain-expressed extrasynaptic receptors. Schild analysis of 018 at recombinant human ?₄?₁? receptors and displacement of [³H]muscimol binding in rat cortical homogenate independently confirmed a competitive profile. The antagonist profile of 018 was further validated by whole-cell patch-clamp electrophysiology, where kinetic studies revealed a slow dissociation rate and a shallow hill slope was observed. Membrane permeability studies showed that 2027 and 018 do not cross membranes, thus making the compounds less attractive for studying central GABA_? receptors effects, but conversely more attractive as tool compounds in relation to emerging peripheral GABA_? receptor-mediated effects of GABA e.g. in the immune system.

SUBMITTER: Falk-Petersen CB 

PROVIDER: S-EPMC7308271 | biostudies-literature | 2020 Jun

REPOSITORIES: biostudies-literature