Research Article

Ouabain-Induced Apoptosis in Cochlear Hair Cells and Spiral Ganglion Neurons In Vitro

Figure 3

Photomicrographs show SGNs at 24 h following ouabain treatment (0–1000 μM). (a) SGNs were cultured for 24 h in a standard culture medium without ouabain. Note that SGNs and auditory nerve fibers were intact. (b) 50 μM ouabain treatment for 24 h caused condensation of the body in some SGNs. (c) 500 μM ouabain for 24 h resulted in soma condensation or fragmentation in most SGNs. (d) All SGNs and auditory nerve fibers were destroyed 24 h after 1000 μM ouabain treatment (fluorescence microscope magnification ×600). Specimens were labeled with an antibody directed against neurofilament 200 and Alexa Fluor 555 conjugated secondary antibody (red). (e) At 24 h after culture with standard medium without ouabain, all SGNs were intact. (f) At 24 h after 500 μM ouabain, 22% SGNs were condensed or shrunk. (g) At 24 h after 500 μM ouabain, the percentage of degenerating SGNs with cell shrinkage was greatly increased with 67% showing degeneration. (h) At 24 h after 1000 μM ouabain, 90% SGNs were present with morphological apoptotic features seen and characteristic cell condensation, cell shrinkage, and/or nuclear/cellular fragmentation.
(a)  0 μM ouabain 24 h
(b) 50 μM ouabain 24 h
(c) 500 μM ouabain 24 h
(d) 1000 μM ouabain 24 h
(e) 0 μM ouabain 24 h
(f) 50 μM ouabain 24 h
(g) 500 μM ouabain 24 h
(h) 1000 μM ouabain 24 h