Modeling the Measurements of Cochlear Microcirculation and Hearing Function after Loud Noise.

摘要

AbstractObjective. Recent findings support the crucial role of microcirculatorydisturbance and ischemia for hearing impairment especiallyafter noise-induced hearing loss (NIHL). The aim of this studywas to establish an animal model for in vivo analysis of cochlearmicrocirculation and hearing function after a loud noise to allowprecise measurements of both parameters in vivo.Study Design. Randomized controlled trial.Setting. Animal study.Subjects and Methods. After assessment of normacusis (0 minutes)using evoked auditory brainstem responses (ABRs), noise(106-dB sound pressure level [SPL]) was applied to both ears in6 guinea pigs for 30 minutes while unexposed animals served ascontrols. In vivo fluorescence microscopy of the stria vasculariscapillaries was performed after surgical exposure of 1 cochlea.ABR measurements were derived from the contralateral ear.Results. After noise exposure, red blood cell velocity wasreduced significantly by 24.3% (120 minutes) and furtherdecreased to 44.5% at the end of the observation (210 minutes)in contrast to stable control measurements. Vesseldiameters were not affected in both groups. A gradual decreaseof segmental blood flow became significant (38.1%) after 150minutes compared with controls. Hearing thresholds shiftedsignificantly from 20.0 ± 5.5 dB SPL (0 minutes) to 32.5 ± 4.2dB SPL (60 minutes) only in animals exposed to loud noise.Conclusion. With regard to novel treatments targeting the striavascularis in NIHL, this standardized model allows us to analyzein detail cochlear microcirculation and hearing functionin vivo.Keywords: Cochlea, stria vascularis, microcirculation, ABR, in vivo fluorescencemicroscopy, animal model, noise-induced hearingloss, NIHL