ABSTRACT
Objective To establish an auditory evoked potential (AEP) detection system in zerbafish.Methods The AEP detection tank was designed and made, and then verified for its quality and reliability via four experiments: anesthesia experiment, swim bladder deflation, noise exposure and goldfish AEP test.Finally, zebrafish (total length form 10 mm to 46 mm) were determined using this system for AEP.Zebrafish randomly were divided into five groups according to total length (TL=12~15 mm, n=6;TL=17~20 mm,n=4;TL=22~26 mm, n=4;TL=32~37 mm, n=9;and TL=42~46 mm,n=12).Goldfish, as control group, were purchased for local petshop (TL=38~54 mm,n=8).Results The results of these four verifying experiments confirmed the biological, rather than artefactual, nature of the responses represented by the recorded waveforms.The AEPs were detected up to a much higher frequency limit (12 kHz) than previously reported.In this study, all fish demonstrated a range of hearing frequency from 100 Hz to 12 kHz without frequency expansion during development.The best hearing was observed at 600 Hz~1 kHz.The mean values of the frequency-averaged thresholds (mean SEM) were 141.7±1.32, 124.8±1.31, 121.8±1.49, 117.8 ±1.09 and 124.4±1.87 dB w, respectively, for the 5 TL groups.The AEP thresholds demonstrated both developmental improvement and age-related loss of hearing sensitivity.Conclusion An auditory evoked potential detection system of zerbafish has been established with stable performance and can be used for AEP detection of zebrafish.
ABSTRACT
Objective To investigate the effects of different doses of diphtheria toxin on cochlear structure and auditory function of adult wildtype mice.Methods The auditory-mature wild type C57BL/6J mice 4 weeks old were randomly devided into 50 ng/g group, 100 ng/g group and control group.C57BL/6J mice in the 50 ng/g or 100 ng/g group were injected 50 ng/g or 100 ng/g diphtheria toxin intraperitoneally for one time, respectively, and the control mice were injected equal volume of normal saline for one time.Then we investigated the ABR threshold change and morphological change of inner and outer hair cell and spiral ganglion neuron 7 days after the injection.Results At 7 day post diphtheria toxin injection compared with those of in control group, in the 50 ng/g group, there was no threshold elevation across frequencies(8 kHz ABR threshold was 20.0±3.78 and 20.83±2.04 dB SPL for 50 ng/g and control respectively), and no loss of inner and outer hair cells (for both groups, the HC loss rates were 0.3%~1%) or SGN (the SGN density was 39.45±3.65, 41.03±3.73/105 μm2, in 50 ng/g and control, respectively).However, the 100 ng/g group, compared with those of in control group, the ABR threshold (8 kHz ABR threshold was 63.0±4.47 dB SPL, respectively)was significantly elevated across each frequency(t=19.62,P<0.001), and there was significant loss of outer hair cell (the loss rate of IHC and OHC was 0.5%±0.1%, 10.7%±0.3%, respectively), which was 10% loss in the apical, middle and basal turn(t=42.219,P<0.001).And the loss of spiral ganglion neuron (the SGN density was 25.55±3.66/105 μm2) was 38%, which was significantly different from the control(t=10.985,P<0.001).Conclusion High dose injection of diphtheria toxin can cause loss of outer hair cell and spiral ganglion neuron in wild type auditory-mature C57BL/6J mice.
ABSTRACT
Cochlear implantation has been a standard therapy for treating severe deafness because patients who receive it have better speech perception. However, the hearing performance of cochlear implantation in noisy environment is far from satisfaction. Efforts have been made to reverse such condition, such as EAS, bimodal stimulation, environment-adaptive speech enhancement and multipolar stimulation, and patients who receive it get more or less better speech perception in noisy environment than traditional cochlear implantation.