title: 2'-Methoxy-6-methylflavone: a novel anxiolytic and sedative with subtype selective activating and modulating actions at GABA(A)  receptors.
abstract: OBJECTIVE
  Flavonoids are known to have anxiolytic and sedative effects mediated via actions on ionotropic GABA receptors. We sought to investigate this further.
  
  
  METHODS
  We evaluated the effects of 2'-methoxy-6-methylflavone (2'MeO6MF) on native GABA(A) receptors in new-born rat hippocampal neurons and determined specificity from 18 human recombinant GABA(A) receptor subtypes expressed in Xenopus oocytes. We used ligand binding, two-electrode voltage clamp and patch clamp studies together with behavioural studies.
  
  
  RESULTS
  2'MeO6MF potentiated GABA at α2β1γ2L and all α1-containing GABA(A) receptor subtypes. At α2β2/3γ2L GABA(A) receptors, however, 2'MeO6MF directly activated the receptors without potentiating GABA. This activation was attenuated by bicuculline and gabazine but not flumazenil indicating a novel site. Mutation studies showed position 265 in the β1/2 subunit was key to whether 2'MeO6MF was an activator or a potentiator. In hippocampal neurons, 2'MeO6MF directly activated single-channel currents that showed the hallmarks of GABA(A) Cl(-) currents. In the continued presence of 2'MeO6MF the single-channel conductance increased and these high conductance channels were disrupted by the γ2(381-403) MA peptide, indicating that such currents are mediated by α2/γ2-containing GABA(A) receptors. In mice, 2'MeO6MF (1-100 mg·kg(-1) ; i.p.) displayed anxiolytic-like effects in two unconditioned models of anxiety: the elevated plus maze and light/dark tests. 2'MeO6MF induced sedative effects at higher doses in the holeboard, actimeter and barbiturate-induced sleep time tests. No myorelaxant effects were observed in the horizontal wire test.
  
  
  CONCLUSIONS
  2'MeO6MF will serve as a tool to study the complex nature of the activation and modulation of GABA(A) receptor subtypes.
authors.affiliation: Faculty of Pharmacy A15, University of Sydney, Sydney, NSW, Australia.
authors.forename: Nasiara
authors.initials: N
authors.lastname: Karim
authors.forename: John
authors.initials: J
authors.lastname: Curmi
authors.forename: Navnath
authors.initials: N
authors.lastname: Gavande
authors.forename: Graham Ar
authors.initials: GA
authors.lastname: Johnston
authors.forename: Jane R
authors.initials: JR
authors.lastname: Hanrahan
authors.forename: M Louise
authors.initials: ML
authors.lastname: Tierney
authors.forename: Mary
authors.initials: M
authors.lastname: Chebib
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects; D002478:Cells, Cultured; D047309:Flavones / Q000494:pharmacology*; D018757:GABA Modulators / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D051379:Mice; D008807:Mice, Inbred BALB C; D009043:Motor Activity / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000502:physiology*; D014982:Xenopus laevis
chemical_list: C572151:2'-methoxy-6-methylflavone; D014151:Anti-Anxiety Agents; D047309:Flavones; D018757:GABA Modulators; D006993:Hypnotics and Sedatives; D011963:Receptors, GABA-A