Potassium circulation in the perilymph of guinea pig cochlea

Abstract

To determine whether any differences exist in potassium circulation between the scala vestibuli and scala tympani, we recorded the change in K⁺ activity in both scalae of the guinea pig cochlea at the basal and third turns, using a double-barrelled, K⁺-sensitive microelectrode after perfusion with artificial perilymph containing 20 mM KCl and 130 mM NaCl. K⁺ activity increased immediately after the start of perfusion and decreased after its completion. The rates of decrease of K⁺ activities were approximately 1.0 mEq/l per min in the scala vestibuli of the basal and third turns, also 1.0 mEq/l per min in the scala tympani of the basal turn, and approximately 0.5 mEq/l per min in the scala tympani of the third turn. The rate of decrease of K⁺ activity in the scala tympani was significantly slower in the third turn than in the basal turn. Blockage of the cochlear aqueduct depressed the rate of decrease of K⁺ activity in the scala tympani more in the basal turn than in the third turn. These results suggest that there is a difference in potassium circulation between the scala vestibuli and scala tympani, and that the cochlear aqueduct plays an important role in potassium circulation in the perilymph of the scala tympani.