Fig. 2

Comparison of the thermal nociceptive thresholds among the groups. Thirty-six rats with BCP were treated with opioids or normal saline twice daily for 7 days. The rats were randomly divided into six groups with different drug regimens (n = 6 per group): M group (10 mg/kg morphine), D1 group (10 mg/kg dezocine), D2 group (1 mg/kg dezocine), MD1 group (10 mg/kg morphine + 10 mg/kg dezocine), MD2 group (10 mg/kg morphine + 1 mg/kg dezocine), and control group (1 mL isotonic saline). All rats underwent thermal pain threshold measurements 30 min after drug administration at 7:30 a.m. PWL: paw withdrawal latency. Data are expressed as the mean ± SEM, and two-way analysis of variance (ANOVA) was used, followed by the Bonferroni test for evaluation. *P < 0.05 compared with the control group. #P < 0.05 compared with the morphine group