2005 Fiscal Year Final Research Report Summary
Inhibitory reflex system by capsaicin-sensitive sensory nerves in lower esophageal sphincter
| Project/Area Number |
15500236
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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 |
Nerve anatomy/Neuropathology
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
KURAMOTO Hirofumi Kyoto Institute of Technology, Faculty of Textile Science, Associate Professor, 繊維学部, 助教授 (30153373)
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| Co-Investigator(Kenkyū-buntansha) |
KADOWAKI Makoto University of Toyama, Institute of Natural Medicine, Professor, 和漢医薬学総合研究所, 教授 (20305709)
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| Project Period (FY) |
2003 – 2005
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| Keywords | capsaicin receptor / sensory nerve / SP / CGRP / esophagus / lower esophageal sphincter / immunohistochemistry / Wistar rat |
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| Research Abstract |
1. We investigated the relationship between one of substance P (SP) receptors, neurokinin 1 receptor (NK1R) and SP containing sensory nerve fibers that is considered to show capsaicin-sensitivity in the rat esophagus. NK1R neurons were the most frequent in the upper esophagus. About 77% of the total NK1R neurons were cholinergic and about 23% were nitrergic, and many of the NK1R neurons that occurred in the lower esophagus were nitrergic. Consequently, it is presumed that SP sensory nerves make synaptic contacts with many NK1R neurons in the lower esophagus and the NK1R neurons innervate the lower esophageal sphincter (LES) to inhibit its movement.
2. To examine what kind of esophageal neurons the vagus innervates, we performed immuno-histochemistry of Fos following electrical stimulation of the cervical vagus. As a result, about 10% of the total neurons in the esophagus expressed Fos. Fos neurons increased from the oral to aboral and they were the most frequent in the lower esophagus, and about 85% of the Fos neurons were nitrergic. These results suggest that the vagus preferentially innervates esophageal nitrergic neurons and the inhibitory reflex system of the LES, which shows a pathway of vagus-esophageal nitrergic neurons-LES, may be present.
3. We applied a retrograde tracing method with Fast Bleu (FB) to examine the distribution and origin of capsaicin receptor, TRPV1, containing nerves in the esophagus. Numerous TRPV1 nerve fibers were found in the esophagus, most of which were SP or CGRP positive. Following injection of FB into the esophageal wall, FB was labeled in some neurons in the dorsal root ganglia (DRG) of C1-L2 and the majority of the labeled neurons were TRPV1 positive, most of which expressed SP or CGRP. These findings suggest that most of TRPV1/SP or CGRP nerves in the esophagus may originate from the DRG neurons expressing TRPV1/SP or CGRP.
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