1997 Fiscal Year Final Research Report Summary
Study on the peripheral mechanism of noiceptor sensitization using excitability test
| Project/Area Number |
08680886
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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 |
神経・脳内生理学
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| Research Institution | Nagoya University, Research Institute of Environmental Medicine |
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Principal Investigator |
MIZUMURA Kazue Nagoya University, Research Institute of Environmental Medicine Professor, 環境医学研究所, 教授 (00109349)
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| Project Period (FY) |
1996 – 1997
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| Keywords | ploymodal receptor / nociceptor / sensitizing mechanism / bradykinin / depolarization / receptive terminal / excitability test |
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| Research Abstract |
To evaluate whether terminal depolarization plays an important role in nociceptor sensitization by inflammatory mediators, excitability test at the receptive cite was carried out. Single fiber activities were recorded in vitro using canine testis-spermatic nerve preparations. Electrical excitability was mapped in the mechanically sensitive area, and excitability test was carried out at the spot where the excitation threshold was the lowest. High K^+ solutions (12,18 mM), which is commonly known to induce depolarization, induced brief discharges with concomitant decrease in excitation threshold (increase in excitability), but no clear dependency on the concentration was observed in this change. Bradykinin (3nM) induced neither discharges nor change in excitation threshold. Bradykinin 10nM or higher induced a decrease in excitation threshold when it induced only small increase in discharges while it induced an increase in excitation threshold when it induced a clear increase in descharges. These results suggest a posaibility that collision of discharges originated from the site where excitability test was carried out and from other receptive cites. To avoid this an intra-electrode perfusion system has been developed, and chemical stimulation to limited area which is exposed to infusion solution was carried out. With this method as well, no decrease in excitation by bradykinin 10muM was observed. It was typical that only short-lasting discharges were induced by bradykinin with this method. Effects of bradykinin at lower concentrations were left open to study. This intra-electrode perfusion method provided a new method for visualizing the receptive terminal fibers with a fluorescent dye.
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