The flavone hispidulin, a benzodiazepine receptor ligand with positive allosteric properties, traverses the blood–brain barrier and exhibits anticonvulsive effects

1. The functional characterization of hispidulin (4′,5,7-trihydroxy-6-methoxyflavone), a potent benzodiazepine (BZD) receptor ligand, was initiated to determine its potential as a modulator of central nervous system activity. 2. After chemical synthesis, hispidulin was investigated at recombinant GABA(A)/BZD receptors expressed by Xenopus laevis oocytes. Concentrations of 50 nM and higher stimulated the GABA-induced chloride currents at tested receptor subtypes (α(1−3,5,6)β(2)γ(2)S) indicating positive allosteric properties. Maximal stimulation at α(1)β(2)γ(2)S was observed with 10 μM hispidulin. In contrast to diazepam, hispidulin modulated the α(6)β(2)γ(2)S-GABA(A) receptor subtype. 3. When fed to seizure-prone Mongolian gerbils (Meriones unguiculatus) in a model of epilepsy, hispidulin (10 mg kg(−1) body weight (BW) per day) and diazepam (2 mg kg(−1) BW per day) markedly reduced the number of animals suffering from seizures after 7 days of treatment (30 and 25% of animals in the respective treatment groups, vs 80% in the vehicle group). 4. Permeability across the blood–brain barrier for the chemically synthesized, (14)C-labelled hispidulin was confirmed by a rat in situ perfusion model. With an uptake rate (K(in)) of 1.14 ml min(−1) g(−1), measurements approached the values obtained with highly penetrating compounds such as diazepam. 5. Experiments with Caco-2 cells predict that orally administered hispidulin enters circulation in its intact form. At a concentration of 30 μM, the flavone crossed the monolayer without degradation as verified by the absence of glucuronidated metabolites