| Project/Area Number |
11470376
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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 |
Morphological basic dentistry
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| Research Institution | Okayama University |
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Principal Investigator |
SUGIMOTO Tomosada Okayama University, Dental School, Professor, 歯学部, 教授 (50135729)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAAI Yuichiro Okayama University, Dental School, Research Associate, 歯学部, 助手 (00158057)
ICHIKAWA Hiroyuki Okayama University, Dental School, Associate Professor, 歯学部, 助教授 (20193435)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2000: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1999: ¥12,900,000 (Direct Cost: ¥12,900,000)
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| Keywords | capsaicin / c-fos / nerve injury / trigeminal nerve / pain / thalamus / IB4 / sprout / 坐骨神経 / 侵害刺激 / 伏在神経 / カプサイシン |
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| Research Abstract |
Newborn rats were given systemic administration of capsaicin and the trigeminal ganglion was cytochemically examined 24 hours later. Capsaicin treatment induced many TUNEL-positive structures in the trigeminal ganglion. Electron microscopy revealed that the TUNEL-positive structures were neuronal cell bodies undergoing apoptosis.
Primary neuronal apoptosis was also induced in newborn rats by the transection of infraorbital nerve. Twenty-four hours after injury, many neurons underwent apoptosis in the trigeminal ganglion ipsilateral to the injury. In addition, neuronal apoptosis was also found in the sensory trigeminal nuclear complex ipsilateral to the injured nerve, and in the thalamus (VPM) contralaterally. These results indicate that peripheral nerve injuries in newborn rats induce chain reaction or cascade of apoptosis of the second and third order sensory neurons that are synaptically linked along the neuroaxis.
Adult rats, that had been capsaicin-treated neonatally, received intraoral noxious stimulation and the sensory trigeminal nuclear complex was examined for neurons with c-Fos protein-like immunoreactivity (fos-neurons). Neonatal capsaicin treatment significantly reduced the number of stimulus-induced fos-neurons in the trigeminal complex.
In adult rats whose sciatic nerve was transected neonatally, the central terminal field of the sciatic primary nociceptors negatively labeled with a lectin IB4 markedly shriveled. Instead, the central representation of nearby intact nerves expanded. Activation of such intact nociceptors induced increased number of fos-neurons. The most dramatic increase was seen in the expanded territories of these nerves. Neonatal peripheral nerve section resulted in central collateral sprouting of nearby uninjured primary neurons. These sprouts invaded the deafferented territory of the dorsal horn and established functional synaptic connections.
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