Effect of bCCI on mu opioid receptor (MOR) staining in superficial dorsal horn. (A) Representative photomicrographs of dorsal horn immunoreactivity for Morphine Receptor (MOR) in sham operated rats (Sham MOR) versus bCCI rats on post-ligation day 15. Scale bar represents 100 μM. (B) Dorsal horn MOR staining densitometry at various postoperative days after bCCI and sham (control) s surgery as a percentage of staining in naive rats. MOR staining decreased, with maximal decrease at day 15 (p < 0.001; F = 51.38; df = 1; Two way ANOVA) and then gradual increase in day 30 (p = 0.004 compared to sham operated rats post hoc Tukey test) and day 45 (p < 0.001; bCCI compared to sham operated rats post hoc Tukey test). MOR was similar to sham operated rats at day 90. Data points are group means +/- SEM.