Abstract
Our previous studies have demonstrated that cold stress or water immersion stress suppressed the splenic natural killer (NK) cytotoxicity, and induced Fos expression in hypothalamic paraventricular nucleus (PVN) and brainstem locus coeruleus (LC). It is well known that adjuvant-induced arthritis is an inflammatory stress. This study was designed to investigate whether splenic NK cytotoxicity is suppressed in adjuvant-induced arthritic rats. Adjuvant arthritis was induced in Sprague-Dawley rats by a single subcutaneous injection of 0.1 ml complete Freund's adjuvant (CFA) into the right hind paw. After CFA injection we could observe the marked edema and inflammation in the paw. On day 3, 7, 14 and 21 after CFA injection, the splenic NK cytotoxicity was measured by 51chromium release assay and Fos immunoreactivity in PVN and LC were detected. The results showed that the splenic NK cytotoxicity of adjuvant-induced arthritic rats significantly decreased compared with control group, and the Fos expression in PVN increased significantly compared with control group on day 3, 7, but without significant effect in PVN on day 14, 21 and in LC on day 3, 7 ,14 ,21. These results suggested that adjuvant-induced arthritis, an inflammatory stress, also suppress the splenic NK cytotoxicity, and the mechanism of the suppression of the splenic NK cytotoxicity is different from that of cold stress or water immersion stress. [Jpn J Physiol 55 Suppl:S233 (2005)]
