Movement of the HRP from the middle ear cavity to the inner ear

Abstract

In order to discuss the permeability of the round window membrane, horseradish peroxidase (HRP) was injected into the middle ear cavity. The normal round window membrane resisted HRP penetration from the middle ear side, but when it became pathological after repeated injections, its permeability increased. In such specimens, HRP reaction products were traced in the cochlea and vestibular sensory cells and in the endolymphatic sac. Although the stria vascularis is impermeable to HRP, the vestivular dark cells were accessible, suggesting that the metabolic activity of the dark cells can be more readily controlled by drug applications through the middle ear cavity. This study showed that drugs and other large molecules injected into the middle ear cavity may reach the endolymphatic sac and alter it functionally.