Fig. 4.

Mu and kappa protein levels are increased in the hippocampus of LgA-H rats after 1 month of forced abstinence and incubated behaviors. a, b, c Quantitative measures and representative images showing Western blot analyses for mu (OPRM1), delta (OPRD1), and kappa (OPRK1) receptor proteins, respectively, in the rat hippocampus. LgA-H rats show increased OPRM1 (a) and OPRK1 (c) receptor protein expression after a month of forced abstinence. b There were no significant changes in OPRD1 receptor protein levels. Individual oxycodone intake showed positive correlation to d OPRM1 and f OPRK1 protein levels in the hippocampus. e There was no significant relationship between the OPRD1 and oxycodone intake. For quantification, Western blotting for OPRM1, OPRD1, and OPRK1 proteins were normalized to cyclophilin B (CYPB) and then analyzed. The values represent means ± SEM (n = 5–6 rats per group). Note the differences in scales on the Y-axis. Key to statistics: *p < 0.05 in comparison to saline rats, ^#p < 0.05 in comparison to ShA rats; ^$p < 0.05 in comparison to LgA-L