title: Effects of high intensity noise on the vestibular system in rats.
abstract: Some individuals with noise-induced hearing loss (NIHL) also report balance problems. These accompanying vestibular complaints are not well understood. The present study used a rat model to examine the effects of noise exposure on the vestibular system. Rats were exposed to continuous broadband white noise (0-24 kHz) at an intensity of 116 dB sound pressure level (SPL) via insert ear phones in one ear for three hours under isoflurane anesthesia. Seven days after the exposure, a significant increase in ABR threshold (43.3 ± 1.9 dB) was observed in the noise-exposed ears, indicating hearing loss. Effects of noise exposure on vestibular function were assessed by three approaches. First, fluorescein-conjugated phalloidin staining was used to assess vestibular stereocilia following noise exposure. This analysis revealed substantial sensory stereocilia bundle loss in the saccular and utricular maculae as well as in the anterior and horizontal semicircular canal cristae, but not in the posterior semicircular canal cristae. Second, single unit recording of vestibular afferent activity was performed under pentobarbital anesthesia. A total of 548 afferents were recorded from 10 noise-treated rats and 12 control rats. Noise exposure produced a moderate reduction in baseline firing rates of regular otolith afferents and anterior semicircular canal afferents. Also a moderate change was noted in the gain and phase of the horizontal and anterior semicircular canal afferent's response to sinusoidal head rotation (1 and 2 Hz, 45°/s peak velocity). Third, noise exposure did not result in significant changes in gain or phase of the horizontal rotational and translational vestibulo-ocular reflex (VOR). These results suggest that noise exposure not only causes hearing loss, but also causes substantial damage in the peripheral vestibular system in the absence of immediate clinically measurable vestibular signs. These peripheral deficits, however, may lead to vestibular disorders over time.
authors.affiliation: PhD Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA; Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Courtney
authors.initials: C
authors.lastname: Stewart
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Adel
authors.initials: A
authors.lastname: Maklad
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Xuehui
authors.initials: X
authors.lastname: Tang
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA; Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Jerome
authors.initials: J
authors.lastname: Allison
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: William
authors.initials: W
authors.lastname: Mustain
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA; Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, USA; Department of Neurology, University of Mississippi Medical Center, Jackson, MS, USA.
authors.forename: Wu
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Department of Otolaryngology & Communicative Sciences, University of Mississippi Medical Center, Jackson, MS, USA; Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS, USA. Electronic address: hozhu@umc.edu.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
mesh_terms: D000818:Animals; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000503:physiopathology*; D008297:Male; D009475:Neurons, Afferent / Q000473:pathology; D009622:Noise / Q000009:adverse effects*; D010037:Otolithic Membrane / Q000473:pathology; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D012027:Reflex, Vestibulo-Ocular; D012399:Rotation; D012665:Semicircular Canals / Q000473:pathology; D014725:Vestibular Nerve / Q000503:physiopathology; D014722:Vestibule, Labyrinth / Q000503:physiopathology*
keywords: Hair cell; Noise; Rat; Vestibular; Vestibular afferent; Vestibulo-ocular reflex (VOR)