title: Ultrastructural and electrophysiologic changes of rat cochlea after irradiation.
abstract: OBJECTIVE
  To determine the acute and subacute cochlear effects of sublethal total body irradiation.
  
  
  METHODS
  The study was designed prospectively as a Sprague-Dawley (SD) rat model with otoacoustic emission measurement.
  
  
  METHODS
  Ten rats and 20 ears were included in the study. Distortion product otoacoustic emission (DPOAE) measurements were performed under ketamine anesthesia before and 1 to 8 weeks after sublethal dose total body irradiation. Eight and six rats survived at the first and eighth week measurements, respectively. The frequency bandwidth was set to 1,067 Hz (referenced to f1) - 9,512 Hz (referenced to f2) (2f1 - f2 = 832 - 6,076 Hz) and eight points were sampled per octave, but low-frequency (<2,549 Hz [referenced to 2f1 - f2]) results were not included in the analysis. Averages were obtained at each frequency, and statistical analysis was performed to compare the pre-and postradiation values. Then, three of the rats were killed for transient electron microscopy (TEM) of the temporal bones.
  
  
  RESULTS
  The posttreatment DPOAEs at almost all frequencies showed a trend toward decline at both the first and eighth weeks, but significant reduction was only detected at 3,600 and 3,961 Hz (referenced to 2f1 - f2) in the first week. TEM of the cochlea revealed ultrastructural changes in the outer hair cells (OHCs) and stria vascularis of the basal turn. The cochlear ganglion nuclei and cochlear nerve axons were unaffected.
  
  
  CONCLUSIONS
  Radiation can affect the cochlea in the acute phase at the mid to high frequencies; further prediction for long-term effects requires longer follow-ups.
authors.affiliation: Department Of Otorhinolaryngology, Ankara Numune Hospital, Turkey.
authors.forename: Halit
authors.initials: H
authors.lastname: Akmansu
authors.forename: Adil
authors.initials: A
authors.lastname: Eryilmaz
authors.forename: Hakan
authors.initials: H
authors.lastname: Korkmaz
authors.forename: Gonca
authors.initials: G
authors.lastname: Sennaroğlu
authors.forename: Müge
authors.initials: M
authors.lastname: Akmansu
authors.forename: Celil
authors.initials: C
authors.lastname: Göçer
authors.forename: Ilkan
authors.initials: I
authors.lastname: Tatar
mesh_terms: D000818:Animals; D003051:Cochlea / Q000528:radiation effects* / Q000648:ultrastructure*; D008297:Male; D008854:Microscopy, Electron; D017084:Otoacoustic Emissions, Spontaneous / Q000502:physiology; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley; D018709:Statistics, Nonparametric; D014916:Whole-Body Irradiation