Loss of Cochlear Ribbon Synapse Is a Critical Contributor to Chronic Salicylate Sodium Treatment-Induced Tinnitus without Change Hearing Threshold
ASR and GPIAS procedures used to measure tinnitus and hearing threshold shifts before and after SS exposure. (a) Sketch map of behavior detection of tinnitus. The rat is startled in the presence of a sudden noise burst (startle stimulus). In normal animals, a silent gap in pure tone background prior to delivery of startle stimulus inhibits the startle response. The rats with putative tinnitus (sound condition is similar to the background tone) exhibit defective behavior. They do not identify the silent gap because of tinnitus. Thus, the startle response is not inhibited in rats with tinnitus, compared to controls without tinnitus. (b) ASR amplitudes of the control (dashed columns, ) and SS-treated (blank columns, ) groups. Average acoustic startle reflex amplitude was significant higher in the treated group than in the control group (). (c) GPIAS values of the control (dashed columns, ) and SS-treated (blank columns, ) groups; between-group differences were significant (). (d) Representative ABR waveforms evoked by pure tone in the SS-treated (upper left) and control (upper right) rats; acoustic intensities are graded from high (90 dB SPL) to low (20 dB SPL). Waveforms are labeled by I, II, III, IV, and V. (e) Statistical analysis of hearing threshold shifts between the SS and control groups across all frequencies tested (2, 4, 8, 12, 16, 20, and 24 kHz); no significant between-group differences were found at any frequency (all ). for the treated group and for the control group.