Age-related hearing loss in the Fischer 344/NHsd rat substrain

Abstract

Studies of the F344 rat have shown a variety of age-related auditory anatomy and physiology changes. The current study was undertaken to clarify the ARHL in the F344 rat, by examining the auditory pathway of the F344/NHsd substrain that is distributed by Harlan Laboratories for research in the United States. The F344/NHsd rat begins to lose its hearing at about 12 months, and by 24 months, there are 50-60 dB auditory brainstem response threshold shifts at 20 and 40 kHz and 20 dB losses at 5-10 kHz. Distortion product otoacoustic emissions (DPOAE) amplitudes at 1.8 to 12 kHz stimuli were depressed in the older (18-24 months) rats. Amplitude input-output functions of the compound action potential (CAP) were also depressed across frequency. The endocochlear potential (EP) was 90-100 mV in the 3 month old rats. All but one of the 24 month old rats' EPs were in the +75-85 mV range. Tympanometry revealed no differences in middle ear function between the young and older rats. Collectively, these findings suggest damage to the outer hair cells, but anatomical examination of the outer hair cells revealed a relative lack of cell loss compared to the magnitude of the hearing and DPOAE loss.

Aging outer hair cells (OHCs) in the Fischer 344 rat cochlea: Function and morphology

“…Although many OHCs in the basal and apical turns were missing, more than 80% of OHCs were still present in the middle 60% turn (20-80%) in the aged rats. The data were consistent with previous reports Bielefeld et al, 2008). IHC loss was only occasionally observed in the aged animals.…”

“…CAP reductions observed at high stimulation levels may be related to the loss of SGCs . Severely suppressed or absent DPOAE in the aged F344 rats further suggested dysfunction of the remaining OHCs Buckiova et al, 2007;Bielefeld et al, 2008).…”

“…The age of 24 months was chosen because the lifespan of the F344 rat is about 30 months with about 87% survival to 24 months (Sass et al, 1975), and the animals show significant hearing loss by that age (Backoff and Caspary, 1994;Bielefeld et al, 2008). Eight young Long Evans rats (2-3 months) were also used for auditory threshold comparison with the young F344 rats.…”

“…Less than 10-20% OHCs or IHCs were missing in aging F344 rats with severe hearing loss Bielefeld et al, 2008). An average of 29% SGC loss was observed in aged rats (Buckiova et al, 2006).…”

Presbyacousie et travail

“…Parmi les facteurs individuels ont trouve (i) les facteurs de risque cardiovasculaires (coronaropathie, AVC, artériopathies des membres inférieurs) [17] (ii) les facteurs hormonaux (rôle néfaste de la progestérone) [18,19], (iii) les facteurs génétiques [20]. Le bénéfice des régimes antioxydants est en cours d'étude avec démonstration ou non d'effets positifs [21][22][23][24][25]. La prise en charge de la presbyacousie doit faire intervenir l'ORL, l'audioprothésiste, le médecin généraliste ou le gériatre, le médecin du travail si le patient est en activité et également l'orthophoniste.…”