title: Insights into functional pharmacology of α₁ GABA(A) receptors: how much does partial activation at the benzodiazepine site matter?
abstract: BACKGROUND
  Synthesis of ligands inactive or with low activity at α₁ GABA(A) receptors has become the key concept for development of novel, more tolerable benzodiazepine (BZ)-like drugs. WYS8, a remarkably (105 times) α₁-subtype selective partial positive modulator, may serve as a pharmacological tool for refining the role of α₁ GABA(A) receptors in mediation of BZs' effects.
  
  
  OBJECTIVE
  Here, the effects of WYS8 on GABA-induced currents and on diazepam-induced potentiation of recombinant BZ-sensitive GABA(A) receptors were studied in more detail. In addition, the behavioral profile of WYS8 (0.2, 1, and 10 mg/kg i.p.), on its own and in combination with diazepam, was tested in the spontaneous locomotor activity, elevated plus maze, grip strength, rotarod, and pentylenetetrazole tests.
  
  
  RESULTS
  WYS8, applied at an in vivo attainable concentration of 100 nM, reduced the stimulation of GABA currents by 1 μM diazepam by 57 % at α₁β₃γ₂, but not at α₂β₃γ₂, α₃β₃γ₂, or α₅β₃γ₂ GABA(A) receptors. The administration of WYS8 alone induced negligible behavioral consequences. When combined with diazepam, WYS8 caused a reduction in sedation, muscle relaxation, and anticonvulsant activity, as compared with this BZ alone, whereas ataxia was preserved, and the anxiolytic effect of 2 mg/kg diazepam was unmasked.
  
  
  CONCLUSIONS
  Hence, a partial instead of full activation at α₁ GABA(A) receptors did not necessarily result in the attenuation of the effects assumed to be mediated by activation of these receptors, or in the full preservation of the effects mediated by activation of other GABA(A) receptors. Thus, the role of α₁ GABA(A) receptors appears more complex than that proposed by genetic studies.
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, 11221, Belgrade, Serbia.
authors.forename: Srđan
authors.initials: S
authors.lastname: Joksimović
authors.forename: Zdravko
authors.initials: Z
authors.lastname: Varagic
authors.forename: Jovana
authors.initials: J
authors.lastname: Kovačević
authors.forename: Michael
authors.initials: M
authors.lastname: Van Linn
authors.forename: Marija
authors.initials: M
authors.lastname: Milić
authors.forename: Sundari
authors.initials: S
authors.lastname: Rallapalli
authors.forename: Tamara
authors.initials: T
authors.lastname: Timić
authors.forename: Werner
authors.initials: W
authors.lastname: Sieghart
authors.forename: James M
authors.initials: JM
authors.lastname: Cook
authors.forename: Miroslav M
authors.initials: MM
authors.lastname: Savić
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000008:administration & dosage / Q000494:pharmacology; D000927:Anticonvulsants / Q000008:administration & dosage / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects*; D002243:Carbolines / Q000008:administration & dosage / Q000494:pharmacology*; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism
chemical_list: C000588763:8-ethynyl-beta-carboline-3-carboxylate-t-butyl ester; D014151:Anti-Anxiety Agents; D000927:Anticonvulsants; D002243:Carbolines; C546242:Gabra1 protein, rat; D011963:Receptors, GABA-A; D003975:Diazepam