Licl reversed the d‐gal‐induced downregulation of Bmi1 in the auditory cortex. (A) Western blot analysis of Bmi1 expression in d‐gal rats vs NS rats. (B) Western blot analysis of Bmi1 expression in 16‐month‐old rats vs 4‐month‐old rats. (C) Western blot showed Bmi1 expression after treatment with Licl. (D) Immunofluorescence assay of Bmi1 expression in 4‐ and 16‐month‐old NS, d‐gal rats, and 16‐month‐old d‐gal + Licl rats. (E) RT‐PCR analysis of Bmi1 in 4‐ and 16‐month‐old NS, d‐gal rats, and 16‐month‐old d‐gal + Licl rats. *P < 0.05, **P < 0.01 (for A–C). *P < 0.05, **P < 0.01 vs NS group. #P < 0.05, ##P < 0.01 vs 4‐month‐old group. ^P < 0.05 vs 16‐month‐old d‐gal group (for D and E, n = 5 for each group).