The Relationships Between The Atrophy Of Stria Vascularis In Inner Ear In Guinea Pigs And Endocochlear Potential

Object: The relationships were studied between the atrophy of stria vascularis and endocochlear potential (EP), and the change of EP was also studied after injection of fursemide by means of the model of the atrophy of stria vascularis in inner ear in guinea pigs. Methods: 58 guninea pigs were used in this experiment.DPOAE,EP and the lenghth of stria vascularis were measured in 29 guninea pigs.EP were measured before and after the injection of fursemide in another 29 guinea pigs DPOAE were measured with Smart OAE 4.32 USBezDP-OAE equipment .The animals were anesthetized and fixed,EP were measured in a shield assembly and monitored by means of a silver/silver-chloride wire electrode filled with 150mM KCl solution. The electrode was inserted through the spiral ligament of the second turn of the cochlea into the cochlear duct by means of a micromanipulator. The EP amplitude of 29 ears were measured before the injection of fursemide and after 60 minutes of injection of fursemide. Morphology: The bulla were quickly removed ,and openings were made in the apex of the cochlea ,the round window and the oval window. After the cochlea was perfused , the stria vascularis and spiral ligament were removed and stained with 0.5% eosin solution for 5 min, then rinsed with water for about 30 min.The whole tissue was mounted on a slide as a flat surface prepartion, examined under a light microscope.The length of the whole stria vascularis and the atrophy of stria vascularis was calculated by pathological image analysis system. Results: There were some of the main feature in the atrophy of stria vascularis: the marginal cell became thin or the quantity of layers decreased; there were only basal cells adjacent to cochlear duct in some locus; the strial vascularis disappeared. All the cochlears in this experiment were continuous areas of atrophy adjacent to normal stria tissue. The mean length of strial atrophy was 3.79mm. The response and amplitude of DPOAE did not show a significant difference between the length of strial atrophy less than 3mm and more than 3mm,p>0.05. The length(ratio) of strial atrophy is related to the EP amplitude,p<0.01.The EP declined rapidly after injection of fursemide, droping from 70.17mV to –36.45mV over the first 5 min,then began to recover at a slow rate. At 60 min post fursemide, the EP had recovered to approximately one third of its original value.The EP recovery ratio of longer strial atrophy was statistically less than the shorter strial atrophy,p<0.01. Conclusion: There were strial atrophy in stria vascularis in inner ear in guinea pigs. The atrophy of stria vascualris can result in the change of EP ,and the guinea pigs with longer atrophy stia vascularis were probably suspectable to fursemide.