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Salicylate decreases the spontaneous firing rate of guinea pig auditory nerve fibres

Research output: Contribution to journalArticlepeer-review

Mark N. Wallace, Christian J. Sumner, Joel I. Berger, Peter A. McNaughton, Alan R. Palmer

Original languageEnglish
Article number135705
JournalNeuroscience Letters
Volume747
DOIs
Published16 Mar 2021

Bibliographical note

Funding Information: This work was supported by the Medical Research Council grant [ MC_U135097127 ] and Action on Hearing Loss grant [ TRIH 2018 ] to CJS and PAM respectively. The funders had no role in study design, data collection and analysis, or decision to publish. Dr T.M. Shackleton developed customised software. Publisher Copyright: © 2021 The Author(s) Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

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Abstract

Tinnitus has similarities to chronic neuropathic pain where there are changes in the firing rate of different types of afferent neurons. We postulated that one possible cause of tinnitus is a change in the distribution of spontaneous firing rates in at least one type of afferent auditory nerve fibre in anaesthetised guinea pigs. In control animals there was a bimodal distribution of spontaneous rates, but the position of the second mode was different depending upon whether the fibres responded best to high (> 4 kHz) or low (≤4 kHz) frequency tonal stimulation. The simplest and most reliable way of inducing tinnitus in experimental animals is to administer a high dose of sodium salicylate. The distribution of the spontaneous firing rates was different when salicylate (350 mg/kg) was administered, even when the sample was matched for the distribution of characteristic frequencies in the control population. The proportion of medium spontaneous rate fibres (MSR, 1≤ spikes/s ≤20) increased while the proportion of the highest, high spontaneous firing rate fibres (HSR, > 80 spikes/s) decreased following salicylate. The median rate fell from 64.7 spikes/s (control) to 35.4 spikes/s (salicylate); a highly significant change (Kruskal-Wallis test p < 0.001). When the changes were compared with various models of statistical probability, the most accurate model was one where most HSR fibres decreased their firing rate by 32 spikes/s. Thus, we have shown a reduction in the firing rate of HSR fibres that may be related to tinnitus.

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