The number of oligodendrocytes in the corpus callosum was quantified by Olig2 immunolabeling. Compared to the sham group, the number of Olig2+ cells decreased over time in untreated CCH rats (all P < 0.001, model group sacrificed at 2 and 4 weeks vs. sham group and P < 0.05, model group sacrificed at 2 weeks vs. at 4 weeks). However, the NBP120 group had more Olig2+ cells than the model group at 2 and 4 weeks (P < 0.05 at 2 weeks, P < 0.001 at 4 weeks; Figures 4A,C). We quantified the number of Olig2+/BrdU+ cells as an index of oligodendrocyte regeneration. Compared to untreated CCH rats, those treated with NBP had more Olig2+/BrdU+ cells at 2 and 4 weeks (all P < 0.001, NBP60 or NBP120 vs. model group; Figures 4A,D). Additionally, while Olig2 protein and mRNA levels were lower in model rats than in sham rats at both postsurgery time points (protein level of Olig2: P < 0.01; mRNA level of Olig2: P < 0.001), higher levels were observed in the NBP120 group at 2 weeks (protein level of Olig2: P < 0.05; mRNA level of Olig2: P < 0.001) and at 4 weeks (protein level of Olig2: P < 0.01; mRNA level of Olig2: p < 0.05; Figures 4B,E,F).