Figure 10. ABR analysis and EP measurement in KI mice with a one-time trans-tympanic middle ear injection of KCl solution. (A) ABR thresholds remaining unchanged throughout two weeks after the control injection of NaCl solution (all P>0.05 for both genotypes, two-way ANOVA followed by Bonferroni post-test). (B) More substantial ABR threshold shifts were observed in homozygous mice following a one-time, 150 mM KCl injection, and recovered at day 15 (P>0.05, two-way ANOVA followed by Bonferroni post-test). (C) EPs tested after direct round window membrane application of KCl solution for 10 minutes showing no significant change in both wild-type and homozygous mice (P>0.05, Student’s unpaired t-test with Welch’s correction). Baseline EPs were obtained by pooling data from young individuals less than 20 weeks old in Figure 3. (D) ABR threshold changes at day 5 after KCl injection (ΔThreshold=day 5 Threshold–day 0 Threshold) with a trend of larger threshold shift in homozygous mice (*P=0.047, F(1,7)=5.814 and *P=0.012, F(1,7)=11.332, for 4 kHz and 8 kHz, respectively, two-way ANOVA followed by Bonferroni post-test). (E) Summary of ABR Wave I latency changes (left panel, ΔLatency=averaged day 5 or day 10 Latency - averaged day 0 Latency) and Wave I amplitude changes (right panel, ΔAmplitude=day 5 or day 10 Amplitude at 90dB SPL - day 0 Amplitude at 90dB SPL). A frequency dependent increase in ΔLatency was observed in homozygous mice, especially in the frequency of 22.6 kHz at day 5 (*P=0.011, F(1,7)=11.727, two-way ANOVA followed by Bonferroni post-test). At day 10, latencies of wild-type mice almost recovered to the baseline level, while those of homozygous mice still had a residual latency prolongation at higher frequencies (P>0.05, two-way ANOVA followed by Bonferroni post-test). ΔAmplitude did not show any significant difference in all frequencies between two genotypes both at day 5 and day 10 (right panel, P>0.05, two-way ANOVA followed by Bonferroni post-test). Wave I responses for 32 kHz were missing therefore not included in this analysis.