Auditory-evoked brainstem response (ABR) measurements were performed on rats injected with saline or AGs once daily for 1 week (a), 2 weeks (b), and 3 weeks (c). The results are presented as the means ± SEM (n = 6). *P < 0.05, **P < 0.01, ***P < 0.001 vs. control group. #P < 0.05, ##P < 0.01, ###P < 0.001 vs. GM group.