Change in K+ activity of the scala media produced by vasopressin.

The endocochlear potential (EP) and K+ activity in the scala media were recorded by means of K+-sensitive double-barreled microelectrodes in the second turn of the cochlea of the guinea pig during the perilymphatic perfusion with vasopressin. Vasopressin produced a decrease in K+ activity in the scala media following a decrease in EP. The decrease in K+ activity in the scala media relative to the EP reduction produced by vasopressin was not significantly different from that by perilymphatic perfusion with furosemide. The present results suggest that vasopressin changes the EP by acting on the stria vascularis.