Fig. 1. Time course of cytokines significantly changed by spinal nerve ligation (SNL). The normal value in unoperated animals is indicated by the  dotted line . Significance of changes (  vs. normal) is indicated by & (  P < 0.05), # (  P < 0.01), and $ (  P < 0.001), based on ratio  t tests (on the logs of the values , i.e. , examining the significance of the fold change). See also  table 1. GRO/KC = growth-related oncogene; IL = interleukin; MCP = monocyte chemoattractant protein.