Ouabain Does Not Induce Selective Spiral Ganglion Cell Degeneration in Guinea Pigs

Figure 2

Acoustically evoked auditory brainstem responses (aABRs) were recorded before and after treatment with ouabain. (a+b) Example of an animal treated with 10 mM ouabain revealing a dramatic aABR threshold shift in the right (treated) cochlea (b), while the responses in the left (untreated) cochlea (a) remained normal. (c+d) Example of an animal treated with 1 mM ouabain showing a moderate increase of the aABR threshold in the right (treated) cochlea (d), while the aABR threshold in the left (untreated) cochlea (c) remained normal. (e) Wave I threshold increased substantially after treatment with 1 mM and 10 mM ouabain. There was no significant threshold shift after treatment with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (f) Four days after treatment, wave I amplitudes had also decreased substantially in the cochleas treated with 1 mM and 10 mM ouabain, but not with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (g) Within 4 days after treatment with 1 mM and 10 mM ouabain, wave II threshold increased substantially. There was no significant threshold shift after treatment with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (h) Wave II amplitudes also decreased substantially in the cochleas treated with 1 mM and 10 mM ouabain 4 days after treatment, but not with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (i) Seven days after treatment, wave I thresholds were still substantially elevated in animals treated with 1 mM ouabain. There was no significant threshold shift after treatment with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (j) Wave I amplitudes remained substantially decreased in cochleas 7 days after treatment with 1 mM ouabain. Animals treated with lower concentrations (0.1 mM and 0.01 mM) did not display significant decrease in wave I amplitude. Left (untreated) ears and right ears treated with PBS alone served as control. (k) Wave II thresholds remained substantially elevated in animals 7 days after treatment with 1 mM ouabain. There was no significant threshold shift after treatment with lower concentrations (0.1 mM and 0.01 mM). Left (untreated) ears and right ears treated with PBS alone served as control. (l) Seven days after treatment with 1 mM ouabain, wave II amplitudes remained substantially decreased in these animals. Animals treated with lower concentrations (0.1 mM and 0.01 mM) did not display significant decrease in wave II amplitude. Left (untreated) ears and right ears treated with PBS alone served as control. Thresholds (e, g, i, and k) and amplitudes (f, h, j, and l) are expressed as change (in dB) from pretreatment levels. Differences in amplitudes of contralateral ears between animals treated with 1 mM and 10 mM are within the normal range of the animals. Error bars represent SD; = p ≤ 0.05, = p ≤ 0.01, = p ≤ 0.001.