title: Mutations M287L and Q266I in the glycine receptor α1 subunit change sensitivity to volatile anesthetics in oocytes and neurons, but not the minimal alveolar concentration in knockin mice.
abstract: BACKGROUND
  Volatile anesthetics (VAs) alter the function of key central nervous system proteins but it is not clear which, if any, of these targets mediates the immobility produced by VAs in the face of noxious stimulation. A leading candidate is the glycine receptor, a ligand-gated ion channel important for spinal physiology. VAs variously enhance such function, and blockade of spinal glycine receptors with strychnine affects the minimal alveolar concentration (an anesthetic EC50) in proportion to the degree of enhancement.
  
  
  METHODS
  We produced single amino acid mutations into the glycine receptor α1 subunit that increased (M287L, third transmembrane region) or decreased (Q266I, second transmembrane region) sensitivity to isoflurane in recombinant receptors, and introduced such receptors into mice. The resulting knockin mice presented impaired glycinergic transmission, but heterozygous animals survived to adulthood, and we determined the effect of isoflurane on glycine-evoked responses of brainstem neurons from the knockin mice, and the minimal alveolar concentration for isoflurane and other VAs in the immature and mature knockin mice.
  
  
  RESULTS
  Studies of glycine-evoked currents in brainstem neurons from knockin mice confirmed the changes seen with recombinant receptors. No increases in the minimal alveolar concentration were found in knockin mice, but the minimal alveolar concentration for isoflurane and enflurane (but not halothane) decreased in 2-week-old Q266I mice. This change is opposite to the one expected for a mutation that decreases the sensitivity to volatile anesthetics.
  
  
  CONCLUSIONS
  Taken together, these results indicate that glycine receptors containing the α1 subunit are not likely to be crucial for the action of isoflurane and other VAs.
authors.affiliation: The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, Texas 78712-0159, USA.
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Borghese
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.forename: S Irene
authors.initials: SI
authors.lastname: Oh
authors.forename: Angel
authors.initials: A
authors.lastname: Ho
authors.forename: S John
authors.initials: SJ
authors.lastname: Mihic
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.forename: David M
authors.initials: DM
authors.lastname: Lovinger
authors.forename: Gregg E
authors.initials: GE
authors.lastname: Homanics
authors.forename: Edmond I
authors.initials: EI
authors.lastname: Eger
authors.forename: R Adron
authors.initials: RA
authors.lastname: Harris
mesh_terms: D000375:Aging / Q000502:physiology; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D055724:Electrophysiological Phenomena / Q000187:drug effects; D005998:Glycine / Q000494:pharmacology; D007530:Isoflurane / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008817:Mice, Mutant Strains; D009068:Movement / Q000187:drug effects; D009154:Mutation / Q000502:physiology*; D009474:Neurons / Q000187:drug effects*; D009865:Oocytes / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation; D011650:Pulmonary Alveoli / Q000187:drug effects; D018009:Receptors, Glycine / Q000187:drug effects* / Q000235:genetics*; D014981:Xenopus
chemical_list: D018685:Anesthetics, Inhalation; D018009:Receptors, Glycine; D007530:Isoflurane; D005998:Glycine