Immobilization increases norepinephrine release and reduces NK cytotoxicity in spleen of conscious rat.

The purpose of this study was to investigate whether immobilization stress would affect the cytotoxic activity of natural killer (NK) cells through the changes in norepinephrine release in the spleen. An in vivo microdialysis technique consisting of high-performance liquid chromatography with electrochemical detection was used to examine norepinephrine levels in the spleen of the conscious rat. The results of the physiological and pharmacological manipulations indicated that norepinephrine recovered in the dialysis solution was mainly derived from the nerve terminals of the splenic sympathetic nerve. Immobilization stress rapidly increased norepinephrine levels to 817.4 +/- 181.7% of baseline in conjunction with the suppression of NK cytotoxicity. Both the increased levels of norepinephrine and the immunosuppression of NK cytotoxicity by immobilization stress were significantly attenuated after surgical denervation of the splenic sympathetic nerve. The results suggest that immobilization-induced suppression of splenic NK cytotoxicity is mediated predominantly through enhanced activity of the splenic sympathetic nerve.