GABA_A receptor subtype selectivity underlying anxiolytic effect of 6-hydroxyflavone

6-Hydroxyflavone (6HF), a naturally occurring flavonoid, was previously reported to bind to type A γ-aminobutyric acid (GABA_A) receptors benzodiazepine (BZ) site with moderate binding affinity. In the present study, we showed that 6HF partially potentiated GABA-induced currents in native GABA_A receptors expressed in cortical neurons via BZ site, as the enhancement was blocked by the antagonist flumazenil. Furthermore, in patch clamp studies, 6HF displayed significant preference for α₂- and α₃-containing subtypes, which were thought to mediate anxiolytic effect, compared to α₁- and α₅-containing subtypes expressed in HEK 293T cells. In mice, 6HF exhibited anxiolytic-like effect in the elevated plus-maze test, unaccompanied at anxiolytic doses by the sedative, cognitive impairing, myorelaxant, motor incoordination and anticonvulsant effects commonly associated with classical BZs when tested in the hole-board, step-through passive avoidance, horizontal wire, rotarod, and pentylenetetrazol (PTZ)-induced seizure tests, respectively. The findings therefore identified 6HF as a promising drug candidate for the treatment of anxiety-like disorders.