Figure 7.

Auditory function and OHC connectivity after a second noise exposure in WT mice. Seven days after AT, WT mice were traumatized again with the same acoustic protocol (n = 6 animals). a, ABR thresholds of WT control, 1 d after AT (AT + 1d), AT + 7d, 1 d after a second noise exposure (2AT + 1d), and 7 d after the second trauma (2AT + 7d). There were large threshold elevations both the day after the first and the second AT with a complete recovery 7 d after either acoustic overexposure. Median and interquartile ranges are shown, and the comparisons were made by Friedman tests followed by a post hoc test. Gray asterisks represent the statistical significance of AT + 7d values compared with 2AT + 1d values (*p < 0.05; **p < 0.01). b, Cumulative frequency histograms of MOC innervation patterns after the first and the second noise exposure. Data corresponding to P21 control mice (Ctrl P21) and AT + 7d are the same as shown in Figure 6. After the second noise exposure, there was not any further reduction in the number of MOC synapses to OHC. We also showed the quantification of MOC terminals in unexposed P35 control (Ctrl p35) mice and found no difference compared with unexposed ctrl P28 mice.