Zusammenfassung
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 ...
Zusammenfassung
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 (alpha(1-3,5,6)beta(2gamma2)S) indicating positive allosteric properties. Maximal stimulation at alpha(1)beta(2)gamma(2)S was observed with 10 muM hispidulin. In contrast to diazepam, hispidulin modulated the alpha(6)beta(2)gamma(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 muM, the flavone crossed the monolayer without degradation as verified by the absence of glucuronidated metabolites.
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