Morphological Changes Induced by Administration of a Na+,K+-ATPase Inhibitor in Normal and Hydropic Inner Ears of the Guinea Pig

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Abstract
The objective of this study was to determine the effects of ouabain, a Na+,K+-ATPase inhibitor, in inner ears. Administering ouabain locally through the round window and vestibule, resulted in degenerative changes in cochlear and vestibular sensory cells and limbal fibrocytes, but the stria vascularis and spiral ligament were less affected. The position of Reissner's membrane was rarely changed. Vacuolar spaces in the sensory epithelia of cristae, maccula utriculi and macula sacculi increased in number. Nystagmus was a common occurrence with or without demonstrating degeneration of vestibular sensory cells. By administering ouabain systemically, the course of developing endolymphatic hydrops could not be altered in the ears with endolymphatic duct blockage. Edema of nerve endings of inner hair cells and vestibular sensory cells was frequently observed with administration of a high concentration of ouabain in both normal and hydropic ears, but edema was reversible. Degeneration of some vestibular sensory cells were observed in hydropic ears with a long survival time. The mechanism of selective sensitivity or non-sensitivity of inner ear tissues to ouabain is discussed.