A. Yu. Abramova - Ph.D. (Med.), Senior Research Scientist, P.K. Anokhin Institute of Normal Physiology (Moscow). E-mail: nansy71@mail.ru

Currently the evidence on the role of immune mechanisms in the development of pain syndromes is accumulated. However, there are only a few details about the correlations between immune status and nociception in mammals. In a study of the participation of immune factors in pain sensitivity special attention is paid to cytokines - mediators of the cell-to-cell interaction. Their production is a part of the cell response, which connected with immunocompetent cells recognition the structure components of various pathogens  pathogen-associated molecular patterns. Such structures, for example, are lipopolysaccharides (LPS) of Gram-negative bacteria. LPS-modulating effect on the nociceptive response allows the administration of the antigen as an optimal model for the experimental study of the mechanisms of nociception. Our study was disigned to evaluate the participation of immune processes in the dynamics of the formation of the various components of nociceptive reactions in rats during peripheral and central administration of LPS. We showed that nociceptive sensitivity of rats increased after i.p. injection of LPS. At the first day after antigen influence in animals has been increasing only perceptual, and on the 7th day  both perceptual and emotional components of nociception. It was found that the administration of LPS into the dorsal hippocampus is accompanied by suppression, and in the cingulate region of the brain  enchancement the emotional component of nociception in animals on the 7th day of the study. Our experiments revealed that the level of pro-and anti-inflammatory cytokines in peripheral blood of rats is reduced by first and to a lesser extent on the 7th day after i.p. injection of LPS. It was shown that i.p. injection of LPS in rats is accompanied by specific changes in cytokine levels in the brain tissue of animals at different times of our study. Antigenic effect of LPS in rats led to increased concentration of inflammatory cytokines but did-t affect the level of proinflammatory cytokines in the dorsal hippocampus and cingulate area of the brain. These data illustrate the close functional interaction of immune and nervous processes underlying the regulation of pain sensitivity in mammals.