A total of 18 rats were randomly selected as the sham group that received vehicle (i.e., corn oil) treatment. The remaining 54 rats were randomly assigned to the following three groups after 2VO surgery (n = 18/group): VD model (2VO surgery + vehicle treatment); NBP60 (2VO + 60 mg/kg NBP); and NBP120 (2VO + 120 mg/kg NBP). NBP doses were selected based on our previous study (Niu et al., 2019). Gavage with NBP or vehicle was performed once a day (between 10:00 and 12:00 a.m.) from the day after surgery to the day of sacrifice (2 or 4 weeks post surgery).