title: Effects of substance P during the recovery of hearing function after noise-induced hearing loss.
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.
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan.
authors: Eiju
authors: E
authors: Kanagawa
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan.
authors: Kazuma
authors: K
authors: Sugahara
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan.
authors: Yoshinobu
authors: Y
authors: Hirose
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan.
authors: Takefumi
authors: T
authors: Mikuriya
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan.
authors: Hiroaki
authors: H
authors: Shimogori
authors: Department of Otolaryngology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi 755-8505, Japan. Electronic address: hiro-shi@yamaguchi-u.ac.jp.
authors: Hiroshi
authors: H
authors: Yamashita
mesh_terms: D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D018072:Hair Cells, Auditory, Outer / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D006317:Hearing Loss, Noise-Induced / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D020127:Recovery of Function / Q000187:drug effects* / Q000502:physiology; D012720:Severity of Illness Index; D013373:Substance P / Q000008:administration & dosage*; D013569:Synapses / Q000187:drug effects / Q000473:pathology / Q000502:physiology
chemical_list: D018696:Neuroprotective Agents; D013373:Substance P
keywords: Cochlea; Hair cell; NK-1; Noise-induced hearing loss; Substance P; Synaptic ribbon