Figure 2.

Tamoxifen injection to iCKO mice leads to reduction in connexin 26, elevation of ABR, and DPOAE thresholds and reduction in EP.

(A–C) Whole mounts of the organ of Corti and adjacent SC areas stained for connexin 26 (green, arrows) and F-actin (phalloidin, red) to depict HCs and their borders. (A) Abundant connexin 26 is seen in the inner sulcus area (medial aspect of the organ of Corti, top of image), and the outer sulcus (bottom of image) in control cochlea. In iCKO cochleae, early tamoxifen injection (B) leads to nearly complete loss of connexin 26 (arrow), whereas late injection results in partial loss (C). Scale bar in A (for A–C), 100 μm. (D–I) Deterioration of functional measures seen after both early and late tamoxifen injections in iCKO mice (CKO) compared with uninjected controls (wild-type [WT]) is summarized here; see text for detailed statistical analyses. (D) and (E) Significant elevation of ABR thresholds was seen after both early (D; P1) and late (E; P14) tamoxifen injections (CKO versus WT) at both tested frequencies (p < 0.0001). Loss of hearing was slightly greater in mice injected at the earlier age (P1 CKO [D] > P14 CKO [E], p < 0.05). (F) and (G) Significant elevation of DPOAE thresholds was seen after both early (F; P1) and late (G; P14) tamoxifen injections (CKO versus WT) at both tested frequencies (p < 0.0001). The differences between ages of injection (P1 CKO [F] versus P14 CKO [G]) were not meaningful. (H and I) Significant depression of endocochlear potential was seen after both early (H; P1, p < 0.02) and late (I; P14, p < 0.01) tamoxifen injections (CKO versus WT). Because of large variances and small sample sizes, the difference in loss of function between ages of injection (P1 [H] versus P14 [I]) was not significant (p > 0.05). ∗p < 0.02, ∗∗p < 0.01, and ∗∗∗∗p < 0.001.