Study on the peripheral mechanism of noiceptor sensitization using excitability test

为了评估末端去极化是否在伤害感受器对炎症介质的致敏过程中起重要作用，我们在接受点进行了兴奋性测试。用犬睾丸精索神经制剂体外记录单纤维活性。在机械敏感区绘制电兴奋性图，在激发阈值最低的部位进行兴奋性试验。高K^+溶液（12,18 mM）通常会引起去极化，引起短暂放电，同时激发阈值降低（兴奋性增加），但在这种变化中没有观察到明显的浓度依赖性。缓激肽（3nM）既没有引起放电，也没有引起兴奋阈值的变化。10nM及以上的缓激肽在仅引起放电小幅度增加的情况下引起兴奋阈值降低，而在引起放电明显增加的情况下引起兴奋阈值升高。这些结果表明，放电的碰撞可能来自进行兴奋性试验的地点和其他接受点。为了避免这种情况，一种电极内灌注系统被开发出来，并对暴露在输液溶液中的有限区域进行化学刺激。用这种方法也没有观察到缓激肽10muM的兴奋性降低。缓激肽仅能引起短时间放电。低浓度缓激肽的作用有待研究。这种电极内灌注法为用荧光染料观察接收端纤维提供了一种新的方法。

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.