title: 6-Chloro-3'-nitroflavone is a potent ligand for the benzodiazepine binding site of the GABA(A) receptor devoid of intrinsic activity.
abstract: 6-Chloro-3'-nitroflavone integrates a list of nearly 70 flavone derivatives synthesized in our laboratories. The effects of 6-chloro-3'-nitroflavone on the benzodiazepine binding sites (BDZ-BSs) of the GABA(A) receptor were examined in vitro and in vivo. 6-Chloro-3'-nitroflavone inhibited the [3H]flunitrazepam ([3H]FNZ) binding to rat cerebral cortex membranes with a Ki of 6.68 nM and the addition of GABA to extensively washed membranes did not modify its affinity for the BDZ-BSs (GABA-shift = 1.16+/-0.12). The binding assays performed in rat striatal and cerebellar brain membranes showed that this compound has similar affinity to different populations of BDZ-BSs. Electrophysiological experiments revealed that 6-chloro-3'-nitroflavone did not affect GABA(A)-receptors (GABA(A)-Rs) responses recorded in Xenopus oocytes expressing alpha1beta2gamma2s subunits, but blocked the potentiation exerted by diazepam (DZ) on GABA-activated chloride currents. In vivo experiments showed that 6-chloro-3'-nitroflavone did not possess anxiolytic, anticonvulsant, sedative, myorelaxant actions in mice or amnestic effects in rats; however, 6-chloro-3'-nitroflavone antagonized diazepam-induced antianxiety action, anticonvulsion, short-term, and long-term amnesia and motor incoordination. These biochemical, electrophysiological, and pharmacological results suggest that 6-chloro-3'-nitroflavone behaves as an antagonist of the BDZ-BSs.
authors.affiliation: Instituto de Biología Celular y Neurosciencias, Facultad de Medicina, Buenos Aires, Argentina.
authors.forename: H
authors.initials: H
authors.lastname: Viola
authors.forename: C
authors.initials: C
authors.lastname: Wolfman
authors.forename: M
authors.initials: M
authors.lastname: Marder
authors.forename: J D
authors.initials: JD
authors.lastname: Goutman
authors.forename: M
authors.initials: M
authors.lastname: Bianchin
authors.forename: C
authors.initials: C
authors.lastname: Wasowski
authors.forename: D J
authors.initials: DJ
authors.lastname: Calvo
authors.forename: I
authors.initials: I
authors.lastname: Izquierdo
authors.forename: A C
authors.initials: AC
authors.lastname: Paladini
authors.forename: J H
authors.initials: JH
authors.lastname: Medina
mesh_terms: D000818:Animals; D000927:Anticonvulsants; D003975:Diazepam / Q000494:pharmacology* / Q000627:therapeutic use; D005419:Flavonoids / Q000494:pharmacology*; D005445:Flunitrazepam / Q000378:metabolism*; D018757:GABA Modulators / Q000494:pharmacology*; D058787:GABA-A Receptor Antagonists; D007858:Learning / Q000187:drug effects*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000187:drug effects*; D012640:Seizures / Q000188:drug therapy; D014981:Xenopus
chemical_list: D000927:Anticonvulsants; D005419:Flavonoids; D018757:GABA Modulators; D058787:GABA-A Receptor Antagonists; D011963:Receptors, GABA-A; D005445:Flunitrazepam; D003975:Diazepam