Regulation of inner ear fluid in the guinea pig cochlea after the application of saturated NaCl solution to the round window membrane

The regulation of K+ and Na+ in the inner ear fluid of the guinea pig was s tudied after the application of saturated NaCl solution to the round window membrane. K+ and Na+ activities in the scala tympani increased rapidly and then decreased. K+ activity in the scala media increased immediately, but Naf activity continued to increase during the period of observation. K+ act ivity in the scala vestibuli continued to increase in the observation perio d. Na+ activity in the scala vestibuli increased and then decreased. The en docochlear potential decreased immediately to approximately 20% of its init ial level. Total activities of K+ and Nai increased immediately and then de creased in both the scala tympani and scala media. The total activity of K and Na+ increased slowly and showed no regulatory decrease in the scala ve stibuli. Thus, changing patterns in the total activity of K+ and Na+ were s imilar for the scala tympani and scala media, but not for the scala media a nd the scala vestibuli. Different patterns of K+ and Na+ activities among t he three scalae indicate that their mechanisms for regulating inner ear flu id differ.