| Project/Area Number |
15300137
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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 |
Neurophysiology and muscle physiology
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| Research Institution | Teikyo University School of Medicine |
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Principal Investigator |
SAKURAI Masaki Teikyo University, School of Medicine, 医学部, 教授 (30162340)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIOKA Noboru Teikyo University, School of Medicine, 医学部, 助手 (20365985)
MAEDA Hitoshi Teikyo University, School of Medicine, 医学部, 助手 (20349252)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 2004: ¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2003: ¥3,700,000 (Direct Cost: ¥3,700,000)
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| Keywords | Coticspinal tract / Synapse formation / Development / Plasticity / Slice culture / Synapse elimination / NMDA / 臨界期 / 活動依存性 / NMDA受容体 |
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| Research Abstract |
We developed corticospinal projection system with functional synapses in vitro, using slices of the rat sensorimotor cortex and spinal cord (Takuma et al., 2002). In the present study, we found that corticospinal synapses are formed widely in the entire spinal cord until 7 DIV, but those in the ventral side are eliminated and the synapse distribution is restricted to the dorsal side by 14 DIV, as seen in the in vivo adult. This synapse elimination is blocked by an NMDA receptor blocker APV, indicating that this process is activity dependent. Retrograde double labeling of the ventral and dorsal nerve terminals and axon reflex studies showed that the synapse elimination is due to axon branch elimination in the spinal cord rather than cell death of the parent cortical neurons. There is a critical period for the blocking effect of APV : APV has no effect before 6 DIV and after 11 DIV and the effect is irreversible when APV is removed from the medium after 11DIV. This is the first in vitro model for critical period of the developmental plasticity.
We also showed above-mentioned synapse elimination occurred in vivo in a quite similar time course: synapses formed in the ventral spinal cord at P7 are eliminated at P8 -P11. Field EPSPs produced by corticospinal synapses in vitro are largely positive, while those in vivo are negative at active synaptic sites. To confirm the positive field EPSPs in vitro indicate active synaptic sites, we recorded corticospinal synaptic activity with fluorescent voltage sensitive dye We found amplitudes of optical signals and field EPSPs are well correlated.
To study competitive relationship between the ventral and dorsal sides and clarify the site of action of APV, we devised compartmented chamber for slice co-culture system.
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