Ameliorative Effects of Exposing DBA/2J Mice to an Augmented Acoustic Environment on Histological Changes in the Cochlea and Anteroventral Cochlear Nucleus

Abstract

DBA/2J (D2) mice, which exhibit very early progressive sensorineural hearing loss, were treated nightly with an augmented acoustic environment (AAE) initiated before the onset of hearing, and consisting of repetitive bursts of a 70-dB sound pressure level (SPL), 4Y25 kHz noise band. At 55 days of age, AAEtreated mice exhibited less elevation of auditory brainstem response thresholds, fewer missing hair cells, and greatly reduced loss of anteroventral cochlear nucleus (AVCN) volume and neuron number compared to untreated control mice. It was hypothesized that the central neuroprotective effect was associated with increased afferent input to AVCN neurons evoked by the AAE as well as a healthier cochlea.

The effects of acoustic environment after traumatic noise exposure on hearing and outer hair cells

“…Application of AAE in auditory research has a long history and was first employed in mice with genetic agerelated sensorineural hearing loss (Turner and Willott, 1998;Willott and Turner, 1999). A series of studies suggested that AAE can ameliorate the severity and time course of hearing loss as well as OHC loss in C57BL/6J and DBA/2J mice (Turner and Willott, 1998;Willott and Turner, 1999;Willott and Bross, 2004;Willott et al, 2001Willott et al, , 2005Willott et al, , 2006aWillott et al, ,b, 2008). …”

Effects of exposing C57BL/6J mice to high- and low-frequency augmented acoustic environments: Auditory brainstem response thresholds, cytocochleograms, anterior cochlear nucleus morphology and the role of gonadal hormones

“…(i.e., approximately 160μm and 320μm posterior to the rostral pole, respectively). Measurements were made on these two standard frontal sections of each mouse, as in our previous studies (Willott and Bross, 2004;Willott et al, 2005). These sections lie, respectively, within the anterior and posterior divisions of the AVCN in the atlas of Trettel and Morest (2001), where additional cytoarchitectonic details may be found.…”

“…First, treatment with a middle-frequency (MAAE, peak SPL from 8-20 kHz) had ameliorative effects on progressive hearing loss in B6 and other inbred strains (Turner and Willott, 1998;Willott an Turner, 1999;Willott and Bross, 2004;Willott et al, 2001;2005;2006a,b). Vazquez et al (2004) also found evidence of OHC preservation after moderate noise exposure.…”

“…The present study is the latest in a series investigating the effects of treatment with augmented acoustic environments (AAEs) on progressive hearing loss and accompanying anatomical changes in mice of the C57BL/6J (B6), DBA/2J (D2), and other inbred strains of mice that exhibit genetic age-related hearing loss (Turner and Willott, 1998;Willott and Turner, 1999;Willott and Bross, 2004;Willott et al, 2000;2005;2006a,b). Treatment using a middlefrequency noise band AAE (MAAE; peak levels from 8-20 kHz) of moderate intensity (70 dB SPL re: 20μPa) has generally ameliorated age-related hearing loss in several strains.…”

Genetics and Age-Related Hearing Loss

“…In addition, structural improvements induced by the AAE were uncovered in DBAs, including preservation of hair cells and AVCN neurons, and reduction of AVCN volume declines with age (Willott et al 2005 ). Turner and colleagues ( 2013 ) also exposed old (22-23 months) CBA mice to AAEs for 6 weeks, and found structural and functional benefi ts for males, but not females, suggesting infl uences of hormonal differential effects late in life.…”