Imprints of the Tectorial Membrane Following Acoustic Overstimulation and Kanamycin Treatment

Abstract

Normal imprints in guinea pigs were examined mainly using a scanning electron microscope (SEM). Morphological changes in imprints after loading of the conditions mentioned below were also investigated. Imprints observed on the normal tectorial membrane were composed of small concavities lined on a W-shaped line and the W-type was of a V-type in proportion to ascend to the upper turn. The imprints occurred at the rate of one for every outer hair cell and in 3-4 lines corresponding to the outer hair cell hairs. With exposure to a high intensity of sound, small concavities of the imprints were deformed and remnant sensory hairs were observed, sporadically. Another line of new imprints was sometimes evident in the lower turn of the cochlea, in addition to the original imprints. In case of inner ear disturbances due to kanamycin (KM) loading, the imprints were little deformed, but the remnant sensory hairs were numerous and their time-course revealed a gradual decrease and the disposal required a longer time than seen in the degenerated cell fractions on the reticular membrane. With exposure to high intensity sound after KM loading, KM-type changes or high intensity sound-type changes were observed and depended on severity of the KM-induced disturbance. The imprints existed for a considerably long time even when the lower region sensory cells degenerated or disappeared in the presence of various conditions.

Key Words:

• cochlear sensory hair
• tectorial membrane
• ototoxicity
• acoustic trauma
• guinea pig