|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 2. Comparison of age-related hair cell loss and changes in auditory brainstem
response (ABR) thresholds of FBN and F344 rats. (A) Cochleograms of aged F344
(24 months, N=8) and aged FBN (32 months, N=7) rats showing
percent hair cells relative to young rats. The pattern of age-related hair
cell loss was different between the two strains. Aged FBN rats lost few inner
hair cells (IHCs), while aged F344 rats displayed small IHC losses (<10%)
throughout the cochlea with pronounced increase in IHC loss near the basal
end. F344 exhibited U-shaped loss of outer hair cells (OHCs) with the greatest
losses (as high as 70%) confined to apical and basal turns. Low levels of OHC
losses were observed throughout the F344 cochlea. FBN rats had significant OHC
losses starting at the apex, which tapered to moderate losses in the basal
regions. The pattern of OHC loss resembles those described for Brown Norway
spiral ganglion cells (Keithley et al.,
1992). (B) ABR thresholds for young and aged F344 (3 months,
N=28; 24 months, N=18) and FBN rats (4 months,
N=11; 32 months, N=10) are shown. F344 rat thresholds were
lower at 4 and 8 kHz than 16 and 24 kHz. FBN rats displayed a significantly
different threshold pattern, with the lowest thresholds at higher frequencies
(ANOVA, *P<0.01). Aging affected both strains similarly
with near parallel upward threshold shifts. For the FBN strains, age-related
threshold shifts did not correlate with the apical pattern of hair cell loss.
(Adapted from Turner and Caspary,
2005.)
|
