Cochlear pathways

Active and passive barriers and pathways into and within the cochlear duct were of interest to Tonndorf. He investigated them with vital stains. Subsequent studies with ultramicroscopy, tracers, immunohistochemistry, and biochemistry have resulted in few changes in our concepts of cochlear duct compartmentalization. The basilar membrane presents almost no barrier, whereas the tight junctions between cells at the endolymphatic surface do. The inner hair cells are less penetrable than are the outer hair cells. The stria vascularis is the most isolated cell grouping within the cochlear duct. Selective active transport makes many general statements suspect. The differences in the penetration rates of Gentamicin and the more cochleotoxic Neomycin may, in part, explain their relative cochleotoxicity. The rate of penetration of Neomycin into the cochlear duct is more rapid than that of Gentamicin. However, the ultimate distribution of both antibiotics is similar and does not contradict Tonndorf's observations.