A comparison of the reduction in the K+ activity of the scala media produced by furosemide and ouabain.

The endocochlear potential (EP) and the K+ activity in the scala media of the guinea pig were recorded by means of K(+)-sensitive, double-barrelled microelectrodes in the second turn of the cochlea. EP and K+ change were recorded during the perilymphatic perfusion of furosemide and ouabain. Furosemide produced less of a decrease than ouabain in the K+ activity relative to the EP decrease. These results suggest that furosemide reduces the EP via different mechanisms from the inhibition of the K+ secretion potential.