1994 Fiscal Year Final Research Report Summary
Joint Study on Neuroactive Amino Acids in the Inner Ear
| Project/Area Number |
05044145
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Institution | Hirosaki University |
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Principal Investigator |
USAMI Shin-ichi Hirosaki University School of Medicine Associate Professor, 医学部, 助教授 (10184996)
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| Co-Investigator(Kenkyū-buntansha) |
オッターセン ウレ・ペッ オスロ大学, 医学部, 教授
OTTERSEN Ole petter Oslo University Dept.of Anatomy Professor
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| Project Period (FY) |
1993 – 1994
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| Keywords | Inner Ear / Amino acid / Immunocytochemistry / Neurotransmitter |
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| Research Abstract |
The present study is designed to explore the distribution of neuroactive amino acids in the inner ear. Our immunocytochemical results suggested that various neuroactive amino acids are distributed in the inner ear as well as central nervous system (CNS), and these neurotransmitters certainly contribute to the inner ear function (hearing and equilibrium).
Excitatory amino acids, such as glutamate and aspartate were enriched in hair cells, indicating the possibility that these amino acids may be candidates for hair cell transmitters. In contrast, quantitative electron microscopic analysis revealed notable differences between vestibular hair cells and presumed glutamatergic terminals in the CNS.Therefore, it is conceivable that glutamatergic transmission may be carried out differentially in hair cells. Primary afferent neurons (spiral and vestibular ganglion cells) are also immunoreacted with glutamate, indicating that glutamate has an important role in afferent transmission.
GABA-like immu
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noreactivity, found in the efferent nerve fibers in the organ of Corti, may be involved in the efferent neurotransmission.
Concerning taurine, in the organ of Corti, supporting cells, including border cells, inner phalangeal cells, Deiters cells, pillar cells, and Bottcher cells are enriched in taurine-like immunoreactivity (Tau-LI), contrasting sharply with inner and outer hair cells which did not show noteworthy immunolabelling. In the spiral ligament of the cochlea, fibrocytes were also enriched in Tau-LI.in the vestibular periphery, Tau-LI was found in the nerve chalices (afferent nerve endings) distributed in the peripheral region of the endorgans. In both cochlea and vestibular periphery, Schwann cells and endothelial cells of the blood vessels showed a considerable amount of Tau-LI.The distribution of taurine in the inner ear is not compatible with a transmitter function of this amino acid, but rather suggests an involvement in homeostatic functions such as cell volume regulation. Less
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