Isoliquiritigenin, a chalcone compound, is a positive allosteric modulator of GABAA receptors and shows hypnotic effects

► The hypnotic effect of ILTG was fully inhibited by flumazenil, a benzodiazepine antagonist. ► ILTG was, for the first time, characterized as a GABAA-benzodiazepine receptor ligand. ► ILTG (10−5 M) potentiated GABA-evoked currents to 151% of the control level on dorsal raphe neurons. ► The ILTG effect on GABA currents was blocked by 10−7 M flumazenil. ► ILTG exerts a hypnotic effect by positive allosteric modulation of GABAA receptors.