1999 Fiscal Year Final Research Report Summary
Mechanism for specific synapse formation between taste cells and axons
| Project/Area Number |
09470407
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional basic dentistry
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| Research Institution | Asahi University |
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Principal Investigator |
NINOMIYA Yuzo Asahi Univ.Sch.Dentistry, Assistant Prof., 歯学部, 助教授 (50076048)
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| Project Period (FY) |
1997 – 1999
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| Keywords | synapse formation / taste cells and axons / cross regeneration / congenic mice / gurmarin / sweet tasting gene |
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| Research Abstract |
Mechanisms responsible for synaptic connection between sweet-sensitive taste cells and nerve fibers were studied by examining responses of single nerve fibers to sweet substances and their inhibition by gurmarin, a specific inhibitor for sweet responses, in C57BL mice. Sweet responses of the chorda tympani (CT) nerve were inhibited by gurmarin, whereas no such inhibition was observed in those of the glossopharyngeal nerve, suggesting that taste cells located on the anterior tongue region possess gurmarin-sensitivity but those on the posterior region lack the sensitivity. CT nerve fibers predominantly responsive to sucrose (sucrose-best fibers) were divided into two groups, one is sensitive to gurmarin (GS-type) and the other insensitive to it (GI-type). This suggests specific synaptic connection between gurmarin-sensitive or insensitive taste cells and GS or GI-type taste axons. Nextly, we made congenic strain whose dpa locus controling gurmarin-sensitivity was donated form C57BL but other genetic backgrounds were same as those of BALB lacking gurmarin-sensitivity, and found that the congenic strain exhibits gurmarin-sensitivity, and possess GS-type CT fibers. This indicates that genetic induction of gurmarin-sensitivity in the congenic mouse taste cells is accompanied by co-existence of the GS-type fibers. Finally, we examined gurmarin-sensitivity of cross-regenerated CT and glossopharyngeal fibers. Although so far we have obtained little amount of data to make any conclusion, for the time being the obtained results may support the idea that cross regenerated GS-type axons may selectively reinnervate gurmain-sensitive taste cells.
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[Publications] Ninomiya,Y., Imoto,T., Yatabe,A., Kawamura,S., Nakashima,K and Katsukawa,H.: "Enhanced responses of the chorda tympani nerve to nonsugar sweeteners in diabetic db/db mice"Am.J.Physiol.. 274. R1324-R1330 (1998)
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