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Figure 1 Effect of naloxone treatment on the lipopolysaccharide (LPS)-induced macrophage release of tumor necrosis factor- (TNF-) (A) , interleukin (IL)-6 (B) , and monocyte chemoattractant protein (MCP)-1 (C) . Human acute monocytic leukemia cell (THP-1) culture was pretreated for 1 h with the indicated concentrations of naloxone before stimulation with 100 ng/ml LPS. Supernatants were harvested at 24 h for the measurement of TNF-, IL-6, and MCP-1. The results are expressed as mean values ± SD of 3 experiments. *p < 0.05 compared with the LPS-treated cultures. PBS = phosphate-buffered saline.