Functional role of the spiral ligament related to the conchiear recovery

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1. Cell proliferation in spiral ligament of mouse cochlea damaged by dihydrostreptomycin sulfateMany BrdU labeled nuclei in the spiral ligament in the conchlea damaged by dyhydrostreptomycin sulfate were found. The expressions of fibroblast growth factor receptor and connexin 43 were detected in the spiral ligament where BrdU labeled cells were found. These results suggest that the cell proliferation in the spiral ligament may occur after the drug-induced damage, and this process is probably related to the recovery of the cochlear function.2. Effectiveness and utility of chemical labyrinthectomy with streptomycin sulfate using osmotic pumpLabyrinthectomy was performed surgically or chemically with 30% streptomycin sulfate using osmotic pumps in guinea pigs. After treatment, no statistical differnce was observed in the frequency of spontaneous nystagmus and the degree of yaw head tilt between the groups. These data indicate the reliability and efficacy of osmotic pumps, and it might be possible to make guinea pig models using osmotic pumps to predict various grades of damage in the vestibular periphery of humans.3. The role of acidic fibroblast growth factor in recovery of acoustic traumaWe assessed auditory brain stem response (ABR) thresholds to evaluate cochlear function and observed the sensory epithelium using confocal laser-scanning microscopy. After noise exposure (120dB SPL, 5h), the ABR threshold showed an increase of 〜50dB SPL that recovered after 14 days. Cochlear function in aFGF treated ears recovered more quickly than that in control ears. These results suggest that aFGF may play an important role in cochlear recovery after acoustic trauma.