Microtubules and Laminated Structures in Inner Ear Hair Cells

Abstract

Rat vestibular hair cells and adder (a snake) auditory and vestibular hair cells were examined by electron microscopy after various fixations. An albumin/unbuffered osmic acid/unbuffered glutaraldehyde fixation was found to preserve the microtubules well. After this fixation a narrow connection was observed between ster-eocilia rootlets or rootlet-like structures and apical microtubules. A laminated structure formed by rootlet filament or rootlet-like fibres was consistently found in the lower part of the cuticular structure. Similar but isolated laminated bodies (Friedmann bodies) were occasionally observed in the snake auditory organ. Bundles of microtubules from the area below the cuticular structure as well as from the dense reticular lamina stretch down in the hair cells. In the basal part of the cells' microtubules very frequently connect with afferent synapses. A microtubular connection between the stereocilia rootlets or laminated part of the cuticular structure and the synapses is proposed. Vesicles adherent to microtubules may suggest a transport or guidance function for synaptic vesicles.