Volume 8 Issue 1 (pdf) - Andrew John Publishing Inc

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Figure 1. Noise-induced hearing loss may occur without hair cell loss.
Figure 2. Hair cell loss up to 1/3 after styrene exposure may not result in a functional loss.
styrene at a level of 400 mg/kg per day
for 5 days per week for 3 weeks. Almost
all OHCs in the third row in the middle
turn were missing (marked by “3” in
Figure 2A), but CAP input/output
functions (see purple filled circles in
Figure 2B) at the corresponding
frequencies were similar to the control
(open circles) indicating a normal
cochlear amplification with only 2 rows
of OHCs remained. Our data from 50
styrene-exposed rats showed that:
(1) loss of OHCs in the third row
resulted in little or no hearing loss;
(2) further loss of OHCs in the second
row caused an OHC-loss dependent
hearing loss; (3) after loss of OHCs in
the third and second rows, cochlear
amplification was completely gone
leading to a maximal hearing loss of 40
dB. Different from noise-induced
hearing loss, hearing loss caused by
styrene or other industrial solvents may
never be restored.
referenCes
1. Chen GD, McWilliams M and
Fechter LD. Succinate
dehydrogenase (SDH) activity in
hair cells: A correlate for permanent
threshold elevations. Hearing
Research 2000;145:91–100.
2. Chen GD, Fechter LD. The
relationship between noise-induced
hearing loss and hair cell loss in
rats. Hearing Research
2003;177:81–90.
3. Chen GD, Tanaka C, Henderson D.
Relationship between outer hair cell
loss and hearing loss in rats
exposed to styrene. Hearing
Research 2008;243:28–34.
4. Chen GD, Li MN, Tanaka C, et al.
Aging outer hair cells (OHCs) in the
Fischer 344 rat cochlea: Function
and morphology. Hearing Research
2009;248:39–47.
Canadian Hearing Report 2013;8(1):39-40.
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