Fig. 4. Increase of DPOAE in Pax2-Cx26^+/− mice.

(A and B) Spectra of acoustic emission recorded from WT, Cx26^+/−, and Cx26^−/− mice. Mice were 3 months old. DPOAEs were evoked by two-tone stimulation. f₀ = 16 kHz, I₁/I₂ = 60/55 dB SPL. Insets: Large-scale plots of 2f₁-f₂ and f₁ peaks. The peak of DPOAE (2f₁-f₂) in Cx26^+/− mice was increased, but f₁ and f₂ peaks remained the same as those in WT mice. A pink trace in (B) represents spectrum in Cx26^−/− cKO mice. No DPOAE peak is visible. (C) Increase of DPOAE in Cx26^+/− mice in the I/O plot. In comparison with WT mice, I/O function of DPOAE in Cx26^+/− was shifted up to ~10 dB SPL. However, no DPOAE is recordable in Cx26^−/− mice. (D) Gain in distortion product (DP) (2f₁-f₂ re: f₁) in Cx26^+/− and WT mice. DP gain in Cx26^+/− mice was significantly increased by 5 to 10 dB in comparison with WT mice. (E) Increase of prestin expression at outer hair cells (OHCs) in Cx26^+/− mice. Immunofluorescent staining for prestin at the cochlear apical, middle, and basal turn in Cx26^+/− mice appears more intensive than WT mice. (F) Quantitative measurement of prestin labeling in Cx26^+/− and WT mice. The intensity of prestin labeling at the apical, middle, and basal turn in Cx26^+/− mice was separately normalized to the average value at the corresponding turn in WT mice. Prestin expressions at all cochlear turns in Cx26^+/− mice were significantly increased in comparison with those in WT mice. *P < 0.05 and **P < 0.01, two-tailed t test.