Effect of increased perilymphatic pressure on endocochlear potential.

A study was done to determine how increased fluid pressure in the inner ear influences cochlear blood flow. Hydrostatic pressure was applied to the scala vestibuli or scala tympani in guinea pigs. Endocochlear potential, which is sensitive to the lack of oxygen, was measured through the round window membrane or through the stria vascularis. Cochlear blood flow was confirmed by intravenous injection of India ink. When the perilymphatic pressure was raised to a relatively high level, endocochlear potential decreased, ina similar way as in response to anoxia, because of the cessation of the cochlear blood flow. This change was completely reversible upon applications of pressure for brief periods of time. We consider that the cochlear blood flow ceases when the fluid pressure reaches the level of intracochlear arterial pressure.