The relationship between outer hair cell loss and hearing loss in rats exposed to styrene.
Chen-G-D; Tanaka-C; Henderson-D
Abstr 31st Midwinter Res Meet 2008 Feb; 31:173
Outer hair cells (OHCs) are known to contribute to the cochlear amplifier. However, the relationship between cochlear amplification and number of OHC is still unclear. There are examples of normal thresholds with missing OHCs and conversely, elevated thresholds with a normal population of OHCs. Styrene targets OHCs starting from the third row, resulting in apoptotic cell death of the targeted cells. However, the remaining OHCs and IHCs appeared intact. IHC death did not occur until all 3 rows of OHCs were missing. Thus, the styrene-injured cochlea may be a good model for study of the relationship between cochlear amplification and OHC number. Our results showed that loss of OHCs up to 1/3 caused only a slight permanent threshold shift (PTS). in some cases, 1/3 of OHCs were missing without any observable biological consequences, indicating that normal cochlear amplification does not require a complete set of OHCs and 2/3 of normally functioning OHCs are sufficient to maintain normal cochlear sensitivity. When OHC loss increased from 1/3 to 2/3, PTS increased gradually to about 40 dB. the hearing loss did not continue to increase with OHC loss in the range from 2/3 to 100%. The data indicate that the gain of the cochlear amplifier is not 'all or none' in a certain range (1/3 to 2/3 OHC loss), the gain is OHC number dependent.
Noise-exposure; Exposure-levels; Noise-induced-hearing-loss; Noise-exposure; Noise; Hearing; Hearing-disorders; Hearing-loss; Laboratory-animals; Animals; Styrenes; Exposure-levels; Cell-damage; Cell-function; Cellular-function
Abstracts of the 31st Midwinter Research Meeting
Washington University, St. Louis