Objective To investigate the expression of high-mobility group box 1(HMGB1) in rats after status epilepticus and the effects of HMGB1 inhibitor glycyrrhizic acid on the blood-brain barrier of rats after status epilepticus.Methods Sprague-Dawley rats were randomly divided into 3-h control group, 3-h epilepticus group, 24-h epilepticus group, and 72-h epilepticus group, with 8 rats in each group. After the status epilepticus model was established in epilepticus groups, rats were sacrificed at 3, 24, and 72 hours, respectively, after successful establishment of the status epilepticus model, while the rats in the 3-h control group were given injection of normal saline at corresponding time points and were sacrificed 3 hours after pilocarpine injection. Then the hippocampus tissues from all rats were collected, and Western blot was applied to measure the expression of HMGB1. Rats were randomly divided into control group, epilepticus group, and glycyrrhizic acid treatment group (GA 30 mg/kg), with 8 rats in each group, and the measures above were applied to establish the model in epilepticus group and glycyrrhizic acid treatment group. In addition, the rats in glycyrrhizic acid treatment group were given intraperitoneal injection of glycyrrhizic acid 30 mg/kg 2 hours after successful establishment of epilepticus model, and the rats in the other two groups were given injection of normal saline at corresponding time points. The rats in 3 groups were all sacrificed 24 hours after successful establishment of epilepticus model, and brain tissues were collected to measure Evans blue seepage.Results The expression of HMGB1 in the 3-h epilepticus group increased significantly compared with that in the 3-h control group (P<0.05); the expression of HMGB1 in the 24-h epilepticus group increased further compared with that in the 3-h epilepticus group (P<0.05), while the expression of HMGB1 in the 72-h epilepticus group decreased significantly compared with that in the 24-h epilepticus group (P<0.05). As for Evans blue seepage, at 24 hours after status epilepticus, Evans blue seepage in epilepticus groups increased significantly compared with that in the control group (P<0.05), and Evans blue seepage in the glycyrrhizic acid treatment group decreased significantly compared with that in the epilepticus groups (P<0.05).Conclusions Increase in expression of HMGB 1 and blood-brain barrier damage can be observed in rats after status epilepticus, and administration of HMGB 1 inhibitor glycyrrhizic acid can reduce blood-brain barrier damage.