Lipopolysaccharide and IL-1 α activate CNS pathways as measured by NK cell activity

• Published in: Physiology & behavior 1996-03, Vol.59 (3), p.499-504
• Main Authors: Demissie, Sossiena, Rogers, Carolyn F., Hiramoto, Nancy S., Ghanta, Vithal K., Hiramoto, Raymond N.
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry and metabolism; Biological and medical sciences; Camphor - pharmacology; Camphor odor; Central nervous system; Central Nervous System - cytology; Central Nervous System - drug effects; Cisterna Magna; CNS pathways; Conditioning; Conditioning, Classical - drug effects; Endotoxins - administration & dosage; Endotoxins - pharmacology; Female; Fundamental and applied biological sciences. Psychology; Injections; Injections, Intravenous; Interleukin-1 - administration & dosage; Interleukin-1 - pharmacology; Interleukin-1α; Killer Cells, Natural - drug effects; Lipopolysaccharide; Lipopolysaccharides - administration & dosage; Lipopolysaccharides - pharmacology; Mice; Mice, Inbred BALB C; Neural Pathways - drug effects; NK Cell activity; Spleen - cytology; Spleen - drug effects; Stimulation, Chemical; Vertebrates: nervous system and sense organs
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/0031-9384(95)02091-8

The effect of lipopolysaccharide (LPS) on murine unstimulated and prestimulated natural killer (NK) cells and its ability to serve as an unconditioned stimulus was investigated. LPS injection induced a statistically significant increase in NK cell activity when compared with saline-treated control groups. To demonstrate the existence of communication between the peripheral immune system and the central nervous system (CNS), we used a single-trial conditioning paradigm in which camphor served as the conditioned stimulus (CS) and LPS as the unconditioned stimulus (US). Once a CS/US association is made, exposure of animals to the CS alone results in the conditioned response (i.e., increase in NK cell activity). Using 50 μg of LPS as the US produced a low but significant increase in NK cell activity when compared to control groups. However, 10 μg of LPS did not show a significant increase in NK cell activity. We also observed that interleukin-1 α (IL-1α) injected intracisternally can serve as a US to condition a central neuroendocrine pathway. Because the dose of IL-1α employed was too small to raise NK cell activity in the spleen, the NK cells themselves were formally not subjected to conditioning. These observations suggest that LPS and IL-1α conditions the brain and that NK cell activity can be used as an indicator system to detect neuroendocrine signals arising from the activated pathway(s).