Gene expression study. (a) Tissue injury resulted in the down-regulation of gene expression of nNOS 2.4-fold in the placebo group and 3.4-fold in the ketorolac group. eNOS was insignificantly up-regulated in the placebo group, but down-regulated in the ketorolac group, with significant difference between the two treatment groups. The changes in gene expression following tissue injury were assessed by qRT-PCR. The gene expression level is expressed as fold change relative to pre-surgery level. *indicates p = 0.02; **indicates p = 0.0003 compared to pre-surgery group (paired t-test); #indicates p = 0.026 compared to the placebo group (independent-sample t test). (b & c) The relative changes in gene expression (RQ) from qRT-PCR of eNOS and nNOS were correlated in the placebo group but not in the ketorolac treated group. The association was examined using Pearson correlation at 3 hours post-surgery.