Effects of vanadate on EP and its distribution in guinea pig cochlea

Effects of sigma-sodium vanadate on endocochlear d.c. potential (EP) and cochlear microphonic potential (CM) were examined and its distribution was observed by an X-ray microanalyzer in the guinea pig cochlea. The perilymphatic space was perfused with 1, 5, and 10 mM solutions of sodium vanadate, using a Harvard Microperfusion pump. By perfusing the scala vestibuli, EP and CM showed a rapid decrease. On the other hand, by perfusing the scala tympani, EP showed an overshoot at first, then a gradual decrease, while CM showed only a gradual decrease. The rates of decrease of EP and CM were dependent upon perfusion time and vanadate concentration. After the electrophysiological examinations, the specimen of the cochlea was observed by X-ray microanalyzer. An accumulation of vanadium was confirmed, especially in the stria vascularis and the hair cells. From the results obtained, the possibility of the responsibility of vanadate for a hypothetical sudden deafness originating in the stria vascularis was discussed.