The influence of the xanthohumol from Humulus lupulus L. on the binding of muscimol-Alexa Fluor 532 (Mu-Alexa), a fluorescently labeled GABAA receptor agonist, was studied by fluorescence correlation spectroscopy. An incubation of hippocampal neurons with 75 nM of xanthohumol increased the specific Mu-Alexa binding by approximately 17%, which was selectively found in GABAA receptor Mu-Alexa complexes with hindered lateral mobility [D(bound2) = (0.11 +/- 0.03) microm2/s] as described with midazolam.