title: A novel cholinergic action of alcohol and the development of tolerance to that effect in Caenorhabditis elegans.
abstract: Understanding the genes and mechanisms involved in acute alcohol responses has the potential to allow us to predict an individual's predisposition to developing an alcohol use disorder. To better understand the molecular pathways involved in the activating effects of alcohol and the acute functional tolerance that can develop to such effects, we characterized a novel ethanol-induced hypercontraction response displayed by Caenorhabditis elegans. We compared body size of animals prior to and during ethanol treatment and showed that acute exposure to ethanol produced a concentration-dependent decrease in size followed by recovery to their untreated size by 40 min despite continuous treatment. An increase in cholinergic signaling, leading to muscle hypercontraction, is implicated in this effect because pretreatment with mecamylamine, a nicotinic acetylcholine receptor (nAChR) antagonist, blocked ethanol-induced hypercontraction, as did mutations causing defects in cholinergic signaling (cha-1 and unc-17). Analysis of mutations affecting specific subunits of nAChRs excluded a role for the ACR-2R, the ACR-16R, and the levamisole-sensitive AChR and indicated that this excitation effect is dependent on an uncharacterized nAChR that contains the UNC-63 α-subunit. We performed a forward genetic screen and identified eg200, a mutation that affects a conserved glycine in EAT-6, the α-subunit of the Na(+)/K(+) ATPase. The eat-6(eg200) mutant fails to develop tolerance to ethanol-induced hypercontraction and remains contracted for at least 3 hr of continuous ethanol exposure. These data suggest that cholinergic signaling through a specific α-subunit-containing nAChR is involved in ethanol-induced excitation and that tolerance to this ethanol effect is modulated by Na(+)/K(+) ATPase function.
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Hawkins
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Ian
authors.initials: I
authors.lastname: Martin
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Kondo
authors.affiliation: Ernest Gallo Clinic and Research Center, University of California, San Francisco, California 94608.
authors.forename: Meredith E
authors.initials: ME
authors.lastname: Judy
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Victoria E
authors.initials: VE
authors.lastname: Brings
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Chung-Lung
authors.initials: CL
authors.lastname: Chan
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: GinaMari G
authors.initials: GG
authors.lastname: Blackwell
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Jill C
authors.initials: JC
authors.lastname: Bettinger
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia 23298 Ernest Gallo Clinic and Research Center, University of California, San Francisco, California 94608 agdavies@vcu.edu.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Davies
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D004361:Drug Tolerance; D000431:Ethanol / Q000494:pharmacology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009119:Muscle Contraction; D009154:Mutation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000235:genetics / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D050494:Vesicular Acetylcholine Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C098140:Acr-2 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; D011978:Receptors, Nicotinic; C082365:Unc-17 protein, C elegans; C493164:Unc-63 protein, C elegans; D050494:Vesicular Acetylcholine Transport Proteins; C099378:acr-16 protein, C elegans; C000599694:eat-6 protein, C elegans; D000431:Ethanol; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Caenorhabditis elegans; ethanol; excitation; nicotinic acetylcholine receptors; tolerance