Protective effect of glycyrrhizin on HMGB1 expression in myocardial I/R injury rats. Statistical analysis of the protective effect of glycyrrhizin on HMGB1 miRNA expression in rats with myocardial I/R injury. Data are presented as the mean ± standard deviation. **P<0.01 vs. the Sham group; ##P<0.01 vs. the NS group. I/R, ischemia/reperfusion; HMGB1, high-mobility group box 1; NS, myocardial I/R injury + non-treated group; 2 mg/kg, myocardial I/R injury + pre-treatment with 2 mg/kg glycyrrhizin group; 4 mg/kg, myocardial I/R injury + pre-treatment with 4 mg/kg glycyrrhizin group; 10 mg/kg, myocardial I/R injury + pre-treatment with 10 mg/kg glycyrrhizin group.