Inbred C57BL/6J mice carry two copies of an age-related hearing loss gene (Ahl). It has been shown that these mice begin losing high-frequency hearing at two months. Several functional studies have reported that the Ahl gene renders mice more susceptible to noise-induced hearing loss (NIHL) than strains which do not carry this gene [e.g., Hear. Res. 93 (1996) 181; Hear. Res. 155 (2001) 82; J. Assoc. Res. Otolaryngol. 2 (2001) 233]. Johnson et al. [Hear. Res. 114 (1997) 83] developed a congenic B6.CAST-+Ahl mouse which carries the wild-type allele from Mus musculus castaneus at the Ahl locus. Five each of young C57BL/6J males and females, and B6.CAST-+Ahl males were exposed to a 4-kHz octave band of noise at 108 dB SPL for 4 h. Non-noise-exposed mice of the same strains and age served as controls. The noise-exposed mice were functionally tested for ABR thresholds and DPOAE levels pre-exposure and three times post-exposure: 0 days to determine the magnitude of temporary threshold shift (TTS); 6 days to determine rate of recovery; and 20 days to determine the magnitude of permanent threshold shift (PTS). At 20 days post-exposure, the animals underwent cardiac perfusion to fix their cochleae. The isolated cochleae were embedded in plastic and dissected into flat preparations. By phase-contrast microscopy, each cochlea was evaluated from apex to base to quantify the losses of hair cells, nerve fibers and stria vascularis and to localize stereocilia damage. Functional data from each mouse were aligned with the cytocochleogram using the frequency-place map of Ou et al. [Hear. Res. 145 (2000) 111; Hear. Res. 145 (2000) 123]. Sizable variation in the magnitude of TTS, PTS and hair-cell loss was found among mice of the same genetic strain. The congenic B6.CAST-+Ahl male mice had significantly less TTS immediately post-exposure than C57BL/6J males or females but not less PTS or hair-cell losses at 20 days post-exposure. These results indicate that, at one month of age, mice carrying two copies of the Ahl gene have an increased susceptibility to TTS from a low-frequency noise before they have any indication of age-related hearing or hair-cell loss. However, this appeared not to be the case for PTS. The Ahl gene appears to play a role in susceptibility to NIHL but, other genes as well as systemic and local factors must also be involved.
Links with this icon indicate that you are leaving the CDC website.
The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
You will be subject to the destination website's privacy policy when you follow the link.
CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website.
For more information on CDC's web notification policies, see Website Disclaimers.
CDC.gov Privacy Settings
We take your privacy seriously. You can review and change the way we collect information below.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
Cookies used to make website functionality more relevant to you. These cookies perform functions like remembering presentation options or choices and, in some cases, delivery of web content that based on self-identified area of interests.
Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data.
Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. These cookies may also be used for advertising purposes by these third parties.
Thank you for taking the time to confirm your preferences. If you need to go back and make any changes, you can always do so by going to our Privacy Policy page.