Effects of substance P during the recovery of hearing function after noise-induced hearing loss

Brain Res. 2014 Sep 25;1582:187-96. doi: 10.1016/j.brainres.2014.07.024. Epub 2014 Jul 24.

Abstract

Substance P (SP) is a widely distributed neurotransmitter in living tissues and is involved in various repair processes. We investigated the possibility that SP may ameliorate cochlear hair cell damage produced by noise exposure. The present study examined the effect of SP in protecting the cochlea from noise damage in guinea pigs exposed to noise after an infusion of SP into the inner ear. Changes in the hearing threshold (auditory brain response, ABR), number of synaptic ribbons, and the appearance of the outer hair cells after noise exposure were analyzed at 2 severity levels of noise-induced hearing loss. The moderate noise-induced hearing loss (110dB, 3h) group showed recovery in the ABR threshold over time, finally reaching a level slightly above pre-exposure levels, with only slight injury to the synaptic ribbons and minimal changes in the appearance of the outer hair cells. Our results indicated that in moderate hearing loss, SP exhibited a protective effect on the inner ear, both functionally and structurally. While the final magnitude of ABR threshold elevation was greater in severe noise-induced hearing loss, the synaptic ribbons and outer hair cells showed signs of severe damage.

Keywords: Cochlea; Hair cell; NK-1; Noise-induced hearing loss; Substance P; Synaptic ribbon.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Auditory Threshold / drug effects
  • Auditory Threshold / physiology
  • Disease Models, Animal
  • Evoked Potentials, Auditory, Brain Stem / drug effects
  • Evoked Potentials, Auditory, Brain Stem / physiology
  • Guinea Pigs
  • Hair Cells, Auditory, Outer / drug effects
  • Hair Cells, Auditory, Outer / pathology
  • Hair Cells, Auditory, Outer / physiology
  • Hearing Loss, Noise-Induced / drug therapy*
  • Hearing Loss, Noise-Induced / pathology
  • Hearing Loss, Noise-Induced / physiopathology
  • Neuroprotective Agents / administration & dosage*
  • Recovery of Function / drug effects*
  • Recovery of Function / physiology
  • Severity of Illness Index
  • Substance P / administration & dosage*
  • Synapses / drug effects
  • Synapses / pathology
  • Synapses / physiology

Substances

  • Neuroprotective Agents
  • Substance P