Research Article

Hsp70/Bmi1-FoxO1-SOD Signaling Pathway Contributes to the Protective Effect of Sound Conditioning against Acute Acoustic Trauma in a Rat Model

Figure 2

ABR click and tone and basilar membrane and OHC loss. (a) Hearing thresholds of click sound from four groups before and after noise exposure (NE vs. Ctrl: , SC+NE vs. NE: ; , animals/group). (b) Hearing thresholds of pure tone from four groups after noise exposure (NE vs. Ctrl: , SC+NE vs. NE: ; , animals/group). Ctrl: control group; SC: sound conditioning group which was exposed to a pure tone of 1 kHz at 85 dB SPL for 24 hours; NE: noise exposure group which was exposed to white noise at 115 dB SPL for 6 hours per day over 2 consecutive days; SC+NE: sound conditioning and noise exposure group which was exposed to a pure tone of 1 kHz at 85 dB SPL for 24 hours, and then 3 hours later, followed by white noise at 115 dB SPL for 6 hours per day over 2 consecutive days. Scanning electron micrographs for OHCs in different turns of basilar membrane from the Ctrl and SC groups (d) as well as the NE and SC+NE groups (e). The lower row pictures are the upper row ones at high magnification. White frames show the enlarged areas; triangular arrows indicate OHC loss. Scale bars represent 10 μm. Percentage of OHC loss in different turns from four groups presented in (c) was analyzed with Tukey’s multiple comparisons test (BaseNE vs. SC+NE: , MiddleNE vs. SC+NE: ; , pictures from 3 animals/group). Scale is showing frequency and percent distance from the apex for rat cochlea according to Muller (1991). The apex turn of the basilar membrane was considered as the low-frequency area of 0 to 30 percent distance from the apex for the cochlea; the middle turn was the middle-frequency area of 30 to 60 percent distance from the apex, and the base turn was the high-frequency area of 60 to 100 percent distance from the apex.
(a)
(b)
(c)
(d)
(e)