Encephalopathy associated with septic shock as well as psychiatric disorders can be caused by the central nervous formation of reactive oxygen species (ROS) associated with inflammation. The systemic application of lipopolysaccharide (LPS, 100 mug/kg i.p.) also serves as a model for major depression and results in enhanced inflammatory processes. which are characterized by the stimulation of microglia or macrophages that then impair normal brain function. The aim of the present study was to analyze the effect of peripherally applied LPS on the central nervous formation of ROS and IL-6 in wild-type mice and in mice lacking the NADPH oxidase Nox2 subunit gp91phox. Microdialysis was performed in the striatum of the mice. Central nervous ROS were detected by electron spin resonance spectroscopy using 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH) as reactant, which was infused via a microdialysis probe. IL-6 was measured in microdialysis samples by an immunoassay. Finally, blood samples were taken by heart puncture to detect IL-6 in plasma. In the wild-type mice, LPS significantly increased the ROS formation in the striatum of wild-type mice and resulted in a significantly enhanced IL-6 production. In the mice lacking the NADPH oxidase Nox2 subunit gp91phox, LPS did not enhance ROS formation, while central IL-6 was significantly increased. IL-6 plasma values were enhanced in both types of mice. In conclusion, the gp91phox-containing NADPH oxidase complex is involved in the central nervous ROS formation after peripheral LPS stimulation and might be a pharmacological target in patients with septic shock.