Ischemic wound healing in WT control or opioid receptor-KO mice—MOPr-KO (A), DOPr- KO (B), and KOPr-KO (C)—treated with PBS or morphine (MS) was measured on days 2, 5, 8, 11, 14, 17, and 20. Percent of wound remaining compared to day 1 is reported. *p<0.05, $p < 0.01, #p < 0.001, †p < 0.0001. Significance was determined by two-way ANOVA with Bonferroni’s multiple comparison (A-C). Each value represents mean ± SEM (n = 8 per group from 4 mice each of anterior and posterior wounding area). Abbreviations: WT, wild-type; KO, knockout; MOPr, mu-opioid receptor; DOPr, delta-opioid receptor; KOPr, kappa-opioid receptor; MS, morphine.