title: Changes in immunoreactivity of orexin-A-positive neurons after intravenous lipopolysaccharide injection.
abstract: BACKGROUND
  Orexins are neuromediators that help regulate many different physiological processes; however, their role in regulating immune system functioning is unclear. This study sought to investigate the distribution of orexin in hypothalamic orexin-containing neurons during the first 6 hours after an intravenous injection of a lipopolysaccharide.
  
  
  METHODS
  Orexin-containing neurons were detected by immunohistochemistry (avidin-biotin) on frontal sections from the brains of intact rats and rats after injections of either saline or lipopolysaccharide.
  
  
  RESULTS
  Analysis of immunohistochemically stained sections (levels 26-32 according to Swanson's atlas) revealed that the main pool of orexin-containing neurons was located at brain levels 28 to 30. No changes were shown in the number of orexin-containing neurons in the hypothalamus of intact animals at different times of a day. Visualization of orexin-containing neurons in the lateral hypothalamus decreased only in 6 hours after an injection of lipopolysaccharide (500 microg/kg body weight) at levels 28, 29, and 30 of the rat brain; this might have been the result of changes in the balance of orexin synthesis and utilization.
  
  
  CONCLUSIONS
  These data suggest that orexin-containing neurons play a role in complex reactions in the brain to lipopolysaccharide application.
authors.affiliation: Department of General Pathology and Pathophysiology, State Research Institute of Experimental Medicine RAMS, Saint-Petersburg, Russia.
authors.forename: Sofia V
authors.initials: SV
authors.lastname: Perekrest
authors.forename: Taissia V
authors.initials: TV
authors.lastname: Abramova
authors.forename: Nataliya S
authors.initials: NS
authors.lastname: Novikova
authors.forename: Yurii V
authors.initials: YV
authors.lastname: Loskutov
authors.forename: Vernon J
authors.initials: VJ
authors.lastname: Rogers
authors.forename: Elena A
authors.initials: EA
authors.lastname: Korneva
mesh_terms: D000818:Animals; D007026:Hypothalamic Area, Lateral / Q000166:cytology / Q000187:drug effects; D007275:Injections, Intravenous; D047908:Intracellular Signaling Peptides and Proteins / Q000276:immunology*; D008070:Lipopolysaccharides / Q000008:administration & dosage* / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000276:immunology*; D009479:Neuropeptides / Q000276:immunology*; D000068797:Orexins; D051381:Rats; D017208:Rats, Wistar
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D009479:Neuropeptides; D000068797:Orexins