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Changes in immunoreactivity of orexin-A-positive neurons after intravenous lipopolysaccharide injection

Sofia V Perekrest, Taissia V Abramova, Nataliya S Novikova, Yurii V Loskutov, Vernon J Rogers, Elena A Korneva

Med Sci Monit 2008; 14(7): BR127-133

ID: 863658

Available online: 2008-07-01

Published: 2008-07-01

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.
Material and Method: 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.

Keywords: Neuropeptides - immunology, Rats, Wistar, Male, Neurons - immunology, Lipopolysaccharides - pharmacology, Intracellular Signaling Peptides and Proteins - immunology, Injections, Intravenous, Rats, Hypothalamic Area, Lateral - drug effects, Animals