Diabetic dysgeusia has been revealed since the first Fox's report (1932). In diabetes mellitus, however, ultrastructural study of the taste buds has not reported yet. In this point of view, the present study was perfomed to investigate morphological changes of the taste buds in foliate papillae in streptozotocin (STZ) induced diabetic rats. Diabetes was induced by intra abdominal injection of STZ (60 mg/kg b. w.). After raising for 3 months, 6 months and 12 months, the foliate papillae were collected and observed by means of electron microscopy. The results were as follows : 1. The taste buds of STZ rats were characterized by swelling cytoplasm, vacuole formation, and enlarged nerve fiber. The swelling taste buds contrasted strikingly with the atrophied foliate papillae in the whole STZ rats group. 2. Vacuole formation and pyknosis were seen in the taste buds in 3-month STZ rat group, and 6-month STZ rat group. Increased lipid droplets and a lot of filament bundles are seen in 12-month STZ rat group. 3. A great number of autophagic vacuoles were recognized morphologically as membranous cytoplasmic body (MCB) and zebra body. 4. Swelling mitochondria, rough ER, Golgi apparatus were observed as change of organelle. 5. Intragemmal fibers were enlarged and myelin-like body appeared in subsurface cisternae (ssc) in the Type II cell. Plasma membrane of the nerve ending degenerated in the afferent synapse in the type III cell. On the contrary, afferent synaptic contacts were observed in 12-month STZ rat group as well. 6. Dense substance in the taste pore decreased remarkably in 3-month STZ. It was suggested environment of taste pore changed in the early stage. With the foliate papillae atrophying, taste pore was apt to show stricture. There were also many imperfolate taste pore in 12-month STZ rat. 7. Diabetes showed strong infectiosity. Many taste pores infected with bacteria were observed. On account of these changes in taste buds and nerve element in STZ rats, functional disorder of taste buds were suggested in diabetes mellitus.

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