Fig. 2. Changes of plasma tumor necrosis factor α (TNF;top ) and interleukin 6 (IL-6;bottom ) at baseline and after injection of endotoxin or saline (mean ± SD). Closed circles, endotoxin group; closed squares, saline control group; open squares, ketamine group; open circles, pretreatment group; open triangle, posttreatment group. #P < 0.05 versus  endotoxin group.