Sann H
Physiologisches Institut, Tierärztliche Hochschule, Hannover, Germany.
Eur J Neurosci. 1998 Apr;10(4):1300-11. doi: 10.1046/j.1460-9568.1998.00141.x.
The mechanosensitivity and chemosensitivity of afferent fibres were investigated in an in vitro preparation of the guinea-pig ureter. Electrophysiological recordings were obtained from 5 U-1 (low mechanical threshold, contraction-sensitive) and 74 U-2 units (high threshold). U-2 units had significant higher levels of spontaneous activity, lower conduction velocities, higher mechanical thresholds (U-1: 7 mmHg; U-2: 39 mmHg), less pronounced phasic responses and longer latencies in the response to distensions than the U-1 units. For chemical stimulation, guinea-pig urine (> 800 mosmol/L), bradykinin and capsaicin were applied intraluminally. The responses of U-1 units mainly corresponded to the contractions induced by the chemical stimulation. The vast majority of the U-2 units were excited by urine, bradykinin (threshold: 0.1-1 microM) and capsaicin (threshold: 0.03-0.3 microM). The responses to urine could be mimicked by high concentrations of potassium ions (> 200 mM), but not by an equiosmolar solution of NaCl, urea and mannitol. Chemical stimulation could also result in a transient sensitization of the U-2 units to mechanical stimuli. In the anaesthetized guinea-pig, pseudo-affective responses could be evoked by ureteric distension (threshold: 30-60 mmHg) and serosal application of capsaicin. Intraluminal application of urine in vivo did not evoke any reactions, suggesting that the responses of the U-2 units to urine might be due to an impaired barrier function of the urothelium in vitro. The data are in agreement with the hypothesis that U-2 units are visceral polymodal nociceptors. Since the U-1 units were also able to encode at least noxious mechanical stimuli, their involvement in visceral nociception cannot be excluded.
在豚鼠输尿管的体外制备中研究了传入纤维的机械敏感性和化学敏感性。从5个U-1（低机械阈值，收缩敏感）和74个U-2单位（高阈值）获得了电生理记录。与U-1单位相比，U-2单位的自发活动水平显著更高，传导速度更低，机械阈值更高（U-1：7 mmHg；U-2：39 mmHg），相性反应不那么明显，对扩张的反应潜伏期更长。对于化学刺激，向管腔内施加豚鼠尿液（>800 mosmol/L）、缓激肽和辣椒素。U-1单位的反应主要对应于化学刺激引起的收缩。绝大多数U-2单位被尿液、缓激肽（阈值：0.1 - 1 microM）和辣椒素（阈值：0.03 - 0.3 microM）兴奋。对尿液的反应可被高浓度钾离子（>200 mM）模拟，但不能被等渗的氯化钠、尿素和甘露醇溶液模拟。化学刺激也可导致U-2单位对机械刺激的短暂敏感化。在麻醉的豚鼠中，输尿管扩张（阈值：30 - 60 mmHg）和浆膜应用辣椒素可诱发假情感反应。体内向管腔内施加尿液未引起任何反应，这表明U-2单位对尿液的反应可能是由于体外尿路上皮屏障功能受损。这些数据与U-2单位是内脏多模式伤害感受器的假设一致。由于U-1单位也能够编码至少有害的机械刺激，因此不能排除它们参与内脏痛觉感受。
