Superficial dorsal horn immunohistochemical staining for CCK. (A) Representative photomicrographs of dorsal horn immunoreactivity for cholecystokinin (CCK) in sham operated rats (Sham CCK) versus bCCI rats on post-ligation day 15. Scale bar represents 100 μM. Medial area of the dorsal horn shows greatest decrease in staining in bCCI rats compared to sham-operated controls. (B) Dorsal horn CCK staining densitometry at various postoperative days compared as a percentage of staining in naïve rats. CCK peptide staining decreased at all the time points studied (p < 0.001; F = 68.3; df = 1; Two way ANOVA). CCK -8 showed decrease in immunoreactivity in day 15 (p = 0.001; post hoc Tukey Test) followed by a slight increase at day 30 (p = 0.02; post hoc Tukey test) and then a marked and consistent decrease thereafter to day 90 compared to sham operated rats (p < 0.001; post hoc Tukey test). Data points are group means +/- SEM.