Abstract
Ouabain, a potent Na+K+-ATPase inhibitor, was found to depress endocochlear potential drastically. Using radioactive ouabain, the binding sites of perilymphatically perfused ouabain was examined. Strong binding was observed in the subepithelial region of the spiral prominence and the surrounding spiral ligament, while moderate activity was observed in the vascular stria. However, a histochemical study revealed that Na+K+-ATPase was localized mainly in the vascular stria, while moderate activity was observed in the subepithelial region of the spiral prominence and the surrounding spiral ligament. These results have two interpretations: ouabain most likely binds with Na+K+-ATPase in the lateral wall tissue of the cochlea when perilymphatically perfused and; ii) there might be a barrier for ouabain between the perilymphatic tissues (spiral ligament+spiral prominence) and the endolymphatic tissue (vascular stria).
