OPRM1 and neoplasm: In the corresponding segment of spinal cord, there were significantly lower MOR mRNA and protein expressions (P < 0.05) in the three tumor-injected groups than in the sham group (P < 0.05), and more MOR mRNA and protein was found in the EA and WAA groups than in the CIBP group, but no significant difference was found between these two groups (P > 0.05), as shown in Fig. 5b1–3.