Effects of K(+)-channel blockers on cochlear potentials in the guinea pig

The effects of different K+ channel blockers, 4-aminopyridine (4-AP), tetraethylammonium (TEA) and quinine, on the various cochlear potentials were observed by the means of perilymph infusion. Each of the three blockers depressed the compound action potential. However, they exerted quite different effects on other cochlear potentials, especially comparing 4-AP, a fast K(+)-channel blocker, with two other blockers. 4-AP induced a significant increase in the magnitude of summating potential, while TEA and quinine decreased it; 4-AP showed no effect on the general endocochlear potential (G-EP, the EP value recorded directly from the scala media, SM) and the negative EP component (N-EP), while TEA and Quinine increased G-EP and decreased the absolute value of N-EP. They also exerted different effects on the EP changes induced by exposure to intense noise. The results indicate the different roles of different K(+)-channels in the generation of cochlear potentials. The relationship of the two components of EP (positive and negative) and the G-EP was discussed.