Fig. 1

Chronological changes in auditory brainstem response (ABR) thresholds and body weights. a Schematic timeline of the experimental protocol. b–d Mean ABR thresholds (± standard errors of the mean) for each time point (b 2 months, c 13 months, and d 16–17 months). Animal numbers were as follows: Wild-type (WT), n = 11; Fat-1, n = 15 in b WT, n = 18; Fat-1, n = 18 in c; and WT, n = 7; Fat-1, n = 5 in d. In the early stage (2 months), ABR thresholds were significantly elevated in Fat-1 mice compared with WT mice in response to stimuli at 4 and 32 kHz (b). In contrast, ABR thresholds of Fat-1 mice were significantly decreased at low-middle frequencies at 13 months (c). Time course of changes in body weight at 2 months (wild-type [WT], n = 11; Fat-1, n = 15), 13 months (WT, n = 18; Fat-1, n = 18), and 16–17 months (WT, n = 7; Fat-1, n = 6) of age. e Body weights of WT and Fat-1 mice were not different in the early stage, but those of Fat-1 mice were significantly decreased at 13 months. No significant difference was observed between the two groups in the later stage (at 16–17 months). P values < 0.05 were considered statistically significant (*). OHC outer hair cell, SGN spiral ganglion neuron, SPL  sound pressure level, SV stria vascularis, ANOVA  analysis of variance, ns no significant difference