title: Acetylcholine in the corneal epithelium of diurnal and nocturnal mammals.
abstract: OBJECTIVE
  To analyze the concentration of acetylcholine (ACh) in the corneal epithelium and aqueous humor of various diurnal and nocturnal mammals.
  
  
  METHODS
  The following species were examined: roe deer, cattle, horse, human, moose, sheep, reindeer, wild boar, polecat, lynx, cat, and rat. ACh was determined by liquid chromatography-tandem mass spectrometry.
  
  
  RESULTS
  ACh was present in significant amounts in the corneal epithelium of all diurnal mammals, the concentrations varying from one species to the next. By contrast, it was not detected in any of the nocturnal tissue samples. None of the species showed detectable amounts of ACh in the aqueous humor.
  
  
  CONCLUSIONS
  The amount of ACh in the corneal epithelium varies from one species to the next, with diurnal species showing significant concentrations and nocturnal species no detectable concentrations.
authors.affiliation: Eye Department, National Hospital, University of Oslo, Norway. a.d.ringvold@klinmed.uio.no
authors.forename: Amund
authors.initials: A
authors.lastname: Ringvold
authors.forename: J Leon E
authors.initials: JL
authors.lastname: Reubsaet
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D002415:Cats; D002417:Cattle; D002845:Chromatography; D002940:Circadian Rhythm / Q000502:physiology*; D019573:Epithelium, Corneal / Q000166:cytology / Q000378:metabolism*; D018397:Equidae; D005289:Ferrets; D006801:Humans; D066298:In Vitro Techniques; D046008:Lynx; D051381:Rats; D017208:Rats, Wistar; D012053:Reindeer; D012756:Sheep; D013045:Species Specificity; D034421:Sus scrofa
chemical_list: D000109:Acetylcholine