title: Effects of arginine vasopressin on auditory brainstem response and cochlear morphology in rats.
abstract: OBJECTIVE
  This study was conducted to evaluate the relationship between hearing and cochlear histopathology after arginine vasopressin administration in rats.
  
  
  METHODS
  A total of 30 Wistar rats were injected with either 0.02 unit/g of arginine vasopressin or the same amount of isotonic saline solution. The initial auditory brain stem response threshold was recorded and additional measurements were made at 10, 30, 60, and 90 min after injection of arginine vasopressin or isotonic saline solution. The threshold for each timepoint was compared with the initial threshold. Histological quantitative assessment of endolymphatic hydrops in the cochlea was performed using light microscopy and assessment of the basal, intermediate, and marginal cells of the stria vascularis was performed with electron microscopy.
  
  
  RESULTS
  The auditory brain stem threshold 60 min after arginine vasopressin injection increased significantly in comparison with the initial threshold (P<0.05). Although the index for endolymphatic hydrops in rats administered arginine vasopressin was not different from that in controls (P>0.05), vacuoles in the intermediate cells were increased significantly in the treated rats (P<0.01).
  
  
  CONCLUSIONS
  Hearing impairment was detected without endolymphatic hydrops in rats administered arginine vasopressin. An increase of vacuoles in the intermediate cells may account for the hearing impairment induced by arginine vasopressin injection.
authors.affiliation: Department of Otorhinolaryngology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. Electronic address: naganuma@kitasato-u.ac.jp.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Naganuma
authors.affiliation: Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. Electronic address: kawahara@nc.kitasato-u.ac.jp.
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Kawahara
authors.affiliation: Department of Otorhinolaryngology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. Electronic address: cjb14540@ams.odn.ne.jp.
authors.forename: Koji
authors.initials: K
authors.lastname: Tokumasu
authors.affiliation: Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. Electronic address: ryou@kitasato-u.ac.jp.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Satoh
authors.affiliation: Department of Otorhinolaryngology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, Japan. Electronic address: okamotom@med.kitasato-u.ac.jp.
authors.forename: Makito
authors.initials: M
authors.lastname: Okamoto
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D001309:Auditory Threshold / Q000187:drug effects; D003051:Cochlea / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D018159:Endolymphatic Hydrops / Q000139:chemically induced* / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects* / Q000502:physiology; D008854:Microscopy, Electron; D051381:Rats; D017208:Rats, Wistar; D013316:Stria Vascularis / Q000187:drug effects / Q000648:ultrastructure; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D014662:Vasoconstrictor Agents; D001127:Arginine Vasopressin
keywords: Arginine vasopressin; Endolymphatic hydrops; Intermediate cell; Meniere's disease; Stria vascularis; Vacuole