FIG. 2.

Type I SGN degeneration after ouabain treatment. A, B SGNs in the middle turn of a young adult CBA/CaJ mouse. The perikarya of type I (I) neurons are surrounded by myelinating Schwann cells (s). C, D Apoptotic-like degeneration (arrowheads) appear in the auditory nerve from the basal turn of a mouse 1 day after ouabain treatment. E, F Schwann cells enclose portions of degenerated SGN cytoplasm or the debris of a vanished SGN (asterisk). G SGNs stained positive for NF 200 (red) in the basal turn of normal mouse ear. H, I Many NF 200⁺ cells are missing in the basal turns of the mice 1 and 3 days post-treatment. J Only a few neurons survived in the basal turn of a mouse 7 days post-treatment. K Mean density of NF 200⁺ SGNs in the apical, middle, and basal turns from control, 1-, 3-, 7-, 14-, and 30-day post-treated ears. Scale bars, 2 μm in A, B, D–F; 5 μm in C; 15 μm in J (applies to G–J).