Electrophysiological assessment and pharmacological treatment of blast-induced tinnitus

PLoS One. 2021 Jan 7;16(1):e0243903. doi: 10.1371/journal.pone.0243903. eCollection 2021.

Abstract

Tinnitus, the phantom perception of sound, often occurs as a clinical sequela of auditory traumas. In an effort to develop an objective test and therapeutic approach for tinnitus, the present study was performed in blast-exposed rats and focused on measurements of auditory brainstem responses (ABRs), prepulse inhibition of the acoustic startle response, and presynaptic ribbon densities on cochlear inner hair cells (IHCs). Although the exact mechanism is unknown, the "central gain theory" posits that tinnitus is a perceptual indicator of abnormal increases in the gain (or neural amplification) of the central auditory system to compensate for peripheral loss of sensory input from the cochlea. Our data from vehicle-treated rats supports this rationale; namely, blast-induced cochlear synaptopathy correlated with imbalanced elevations in the ratio of centrally-derived ABR wave V amplitudes to peripherally-derived wave I amplitudes, resulting in behavioral evidence of tinnitus. Logistic regression modeling demonstrated that the ABR wave V/I amplitude ratio served as a reliable metric for objectively identifying tinnitus. Furthermore, histopathological examinations in blast-exposed rats revealed tinnitus-related changes in the expression patterns of key plasticity factors in the central auditory pathway, including chronic loss of Arc/Arg3.1 mobilization. Using a formulation of N-acetylcysteine (NAC) and disodium 2,4-disulfophenyl-N-tert-butylnitrone (HPN-07) as a therapeutic for addressing blast-induced neurodegeneration, we measured a significant treatment effect on preservation or restoration of IHC ribbon synapses, normalization of ABR wave V/I amplitude ratios, and reduced behavioral evidence of tinnitus in blast-exposed rats, all of which accorded with mitigated histopathological evidence of tinnitus-related neuropathy and maladaptive neuroplasticity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcysteine* / pharmacology
  • Acetylcysteine* / therapeutic use
  • Animals
  • Benzenesulfonates* / pharmacology
  • Benzenesulfonates* / therapeutic use
  • Biomarkers / metabolism
  • Disease Models, Animal*
  • Evoked Potentials, Auditory, Brain Stem / drug effects*
  • Hair Cells, Auditory, Inner / metabolism*
  • Hair Cells, Auditory, Inner / pathology
  • Hearing Loss, Noise-Induced* / drug therapy
  • Hearing Loss, Noise-Induced* / physiopathology
  • Male
  • Rats
  • Tinnitus* / drug therapy
  • Tinnitus* / physiopathology

Substances

  • Benzenesulfonates
  • Biomarkers
  • disufenton sodium
  • Acetylcysteine

Grants and funding

This research was supported by the Oklahoma Center for the Advancement of Science and Technology Grant AR14-020. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.