2006 Fiscal Year Final Research Report Summary
Mechanisms for initiation and propagation of calcium signals in glial nets associated with sensory endings: morphological and molecular analysis.
| Project/Area Number |
17590143
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
IWANAGA Hiromi Hokkaido University, Graduate School of Medicine, Associate Professor, 大学院医学研究科, 助教授 (30193759)
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| Project Period (FY) |
2005 – 2006
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| Keywords | mechanoreceptor / sinus hair / terminal Schwann cells / glia / calcium imaging / sensory nerve endings / adenosine 5'-trinhosnhate / rat |
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| Research Abstract |
Stimulus-induced elevations in the intracellular Ca^<2+> concentration ([Ca^<2+>]_i) are known to propagate as waves along cell networks and epithelial sheets for coordination of cell activities. Glial cells associating with sensory endings communicate with one another by their branching processes to constitute networks connecting axon terminals. In order to define the mechanism of initiation and propagation of Ca2+ signals in these glial nets, lanceolate endings that monitor hair movements, were isolated from rat vibrissae, and observed by time-lapse confocal microscopy while the signaling was locally activated by touching the specimen with a fine glass needle. Intercellular coupling by gap junctions was also assessed by the technique of fluorescence recovery after photobleaching (FRAP) and by transmission electron microscopy (TEM). Mechanical stimuli which induced a single-peaked [Ca^<2+>]_i elevation in glial processes covering the perturbed lanceolate were followed by delayed glial
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responses in neighboring 2 to 5 endings. Some of these secondary signals originated from a specific focus in individual glial processes to advance toward the cell body, while others entered the processes through the proximal end of the optical section. The former rapidly spread among glial processes around the stimulation point to involve those lacking physical contacts with the touched cell. The latter, after a delay, affected cytoplasmic extensions of the primarily-activated cell with the propagated signals occasionally traveling into an adjacent glial process. Only the former type of intercellular signaling was inactivated by the purinoceptor blocker suramin. FRAP experiments and TEM observations demonstrated gap junction channels which allow movement of cytoplasmic messengers between the glial processes. These findings indicate that in sensory endings, purinergically-induced glial signals and those potentially dependent on an intracellular messenger are propagated in their own patterns of spatial expansion and time courses to constitute two distinct forms of communication among the receptor axons. Less
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