Glycogen in the Inner Ear After Acoustic Stimulation: A light and electron microscopic study

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Abstract
Glycogen was localized in the inner ear of various species at the light and electron microscopic level. Several techniques of tissue fixation and embedding were tested. Light microscopic demonstration of glycogen was consistent and optimal in glutaraldehyde-fixed and Epon-embedded specimens stained with the periodic acid-Schiff reaction. With this standard method, well-defined intracytoplasmic glycogen granules were red to purple. With the periodic acid-thiosemicarbazide method for electron microscopic demonstration of glycogen, numerous isodiametric electron-dense particles were seen in the same cell regions in which the PAS-positive granules were observed. These electron-dense granules were digestible with α-amylase. The distribution pattern showed marked species differences : in guinea pigs, glycogen granules were limited to the outer hair cells of the cochlea with a decrease basalwards. In mice, most of the glycogen granules were seen in Deiters' cells and less in the outer hair cells. In cats, no glycogen could be demonstrated. In none of these species was glycogen observed in the vestibular sensory and supporting cells. After exposing guinea pigs to 110 dB white noise for 30 minutes, there was a quantitative decrease of glycogen. Three hours after acoustic stimulation numerous smaller granules were detectable and in 12 to 24 hours these aggregated to form bigger granules. Finally, 24 hours after the exposure to noise, the distribution pattern of glycogen reverted to normal. The changes following acoustic stimulation may be due to glycogenolysis and consecutive glycogenesis, suggesting that glycogen serves as an energy source in the hair cells.