[Distribution pattern in the guinea pig cochlea of intravitally injected peroxidase].

Following perilymphatic perfusion and injection into the cisterna cerebello-medullaris, respectively, the distribution pattern of horseradish peroxidase in the cochlea of the guinea pig was studied light and electron microscopically. The findings prove effective tight junctions (zonulae occludentes) between the cells of the epithelial lining of the endolymphatic compartment. At the level of the reticular membrane the tight junctions are far more extended than elsewhere at the cochlear duct epithelium. From the findings a fairly rapid exchange is suggestive between the lymphatic space of the organ of Corti and the tympanic scale. Various types of cells of the cochlear duct actively take up considerable amounts of peroxidase. However, endocytosis of peroxidase by hair cells and particularly by the outer ones is rather scanty. Passive permeation of the tracer through the membran of undamaged hair cells was disproven.