title: Optical reversal of halothane-induced immobility in C. elegans.
abstract: Volatile anesthetics (VAs) cause profound neurological effects, including reversible loss of consciousness and immobility. Despite their widespread use, the mechanism of action of VAs remains one of the unsolved puzzles of neuroscience [1, 2]. Genetic studies in Caenorhabditis elegans [3, 4], Drosophila [3, 5], and mice [6-9] indicate that ion channels controlling the neuronal resting membrane potential (RMP) also control anesthetic sensitivity. Leak channels selective for K(+) [10-13] or permeable to Na(+) [14] are critical for establishing RMP. We hypothesized that halothane, a VA, caused immobility by altering the neuronal RMP. In C. elegans, halothane-induced immobility is acutely and completely reversed by channelrhodopsin-2 based depolarization of the RMP when expressed specifically in cholinergic neurons. Furthermore, hyperpolarizing cholinergic neurons via halorhodopsin activation increases sensitivity to halothane. The sensitivity of C. elegans to halothane can be altered by 25-fold by either manipulation of membrane conductance with optogenetic methods or generation of mutations in leak channels that set the RMP. Immobility induced by another VA, isoflurane, is not affected by these treatments, thereby excluding the possibility of nonspecific hyperactivity. The sum of our data indicates that leak channels and the RMP are important determinants of halothane-induced general anesthesia.
authors.affiliation: Department of Genetics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Vinod K
authors.initials: VK
authors.lastname: Singaram
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Somerlot
authors.forename: Scott A
authors.initials: SA
authors.lastname: Falk
authors.forename: Marni J
authors.initials: MJ
authors.lastname: Falk
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Sedensky
authors.forename: Philip G
authors.initials: PG
authors.lastname: Morgan
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics; D001522:Behavior, Animal; D017173:Caenorhabditis elegans / Q000187:drug effects* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D016825:Chlamydomonas reinhardtii / Q000235:genetics; D059329:Cholinergic Neurons / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006221:Halothane / Q000494:pharmacology*; D007530:Isoflurane / Q000494:pharmacology*; D008027:Light; D008564:Membrane Potentials; D010641:Phenotype; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism; D025604:Rhodopsins, Microbial / Q000378:metabolism; D019782:Riluzole / Q000494:pharmacology; D013045:Species Specificity
chemical_list: D018685:Anesthetics, Inhalation; D024683:Potassium Channels, Tandem Pore Domain; D025604:Rhodopsins, Microbial; D019782:Riluzole; D007530:Isoflurane; D006221:Halothane