Loss of Cochlear Ribbon Synapse Is a Critical Contributor to Chronic Salicylate Sodium Treatment-Induced Tinnitus without Change Hearing Threshold

Figure 4

SS exposure causes swelling of fiber endings of postsynaptic ANs and amplitude changes in ABR wave I. (a) AN fibers were identified using anti-NF200 (green), and cochlear ribbon synapses were identified using anti-CtBP2 (red, blow inner HCs). Massively swollen AN fiber ends with reduced numbers of CtBP2-expressing puncta were evident in the SS group (compared to control group), as shown by white dashed lines (apical turns, left panel) and in enlargements (white circles, right panel). . (b). ABR wave I amplitudes at 2, 4, 8, 12, 16, and 20 kHz. Amplitudes of ABR wave I were found reduced across all the frequencies above (); there were significant differences across frequencies (); in the treated group and in the control group. (c) Cochlear ribbon synapse morphological properties. Synaptic clef was enlarged after SS treatment; there were significant differences in apical, middle, and basal turns (, top). Swelling at the AN terminals was found after SS treatment; there were significant differences in apical, middle, and basal turns (, bottom).

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