Pedersen J L, Andersen O K, Arendt-Nielsen L, Kehlet H
Department of Surgical Gastroenterology, Hvidovre University Hospital, Denmark.
Pain. 1998 Feb;74(2-3):189-97. doi: 10.1016/s0304-3959(97)00162-0.
Temporal summation of pain occurs when repeated stimuli become increasingly painful in spite of unchanged stimulus intensity. Summation can be quantified as the difference in pain between the first and the last stimulus in a train of stimuli. The aim of the study was to compare temporal summation of pain in normal skin with summation of pain in skin with primary and secondary hyperalgesia evoked by a heat injury. A heat injury was produced on the crus of 12 volunteers with a 50 x 25 mm thermode (47 degrees C, 7 min). Measurements were made before, and 0, 1, 2, and 4 h after the heat injury, in three areas: primary and secondary mechanical hyperalgesia induced by the heat injury, and in a mirror image of the injury on the opposite leg. Temporal summation of pain was induced by repeated electrical stimuli (five stimuli at 2 Hz) and assessed by visual analog scale (VAS). Primary hyperalgesia was evaluated by von Frey hairs and electrical stimuli, and the areas of secondary hyperalgesia with a rigid von Frey hair (314 mN). Significant primary (P < 0.000001) and secondary (P < 0.00006) mechanical hyperalgesia were evoked by the heat injury. The pain threshold to single electrical stimuli was reduced within the injury (P < 0.03), but not outside. The pain responses to single and repeated electrical stimuli were not significantly altered by the injury. Temporal summation of pain occurred in 418 stimulus trains out of 576 (73%), but no significant changes in summation developed in skin with primary or secondary mechanical hyperalgesia compared with normal skin (baseline measurements). Temporal summation at high stimulus intensities was more pronounced than at lower intensities (P < 0.0002). We found no correlation between either temporal summation and area of secondary hyperalgesia, or temporal summation and pain intensity during the induction of heat injury. We conclude that the development of primary and secondary mechanical hyperalgesia after heat injury in man was not associated with changes in temporal summation of painful electrical stimuli.
当重复刺激尽管强度不变但却变得越来越疼痛时，就会发生疼痛的时间总和。总和可以量化为一连串刺激中第一个和最后一个刺激之间的疼痛差异。本研究的目的是比较正常皮肤的疼痛时间总和与热损伤诱发的原发性和继发性痛觉过敏皮肤的疼痛总和。使用一个50×25毫米的热探头（47摄氏度，7分钟）在12名志愿者的小腿上造成热损伤。在热损伤前以及损伤后0、1、2和4小时，在三个区域进行测量：热损伤诱发的原发性和继发性机械性痛觉过敏区域，以及对侧腿部损伤的镜像区域。通过重复电刺激（2赫兹的五次刺激）诱发疼痛的时间总和，并通过视觉模拟量表（VAS）进行评估。通过von Frey毛发和电刺激评估原发性痛觉过敏，并用硬von Frey毛发（314毫牛顿）评估继发性痛觉过敏区域。热损伤诱发了显著的原发性（P < 0.000001）和继发性（P < 0.00006）机械性痛觉过敏。损伤部位内对单次电刺激的疼痛阈值降低（P < 0.03），但损伤部位外未降低。损伤并未显著改变对单次和重复电刺激的疼痛反应。在576次刺激序列中有418次（73%）出现了疼痛的时间总和，但与正常皮肤（基线测量）相比，原发性或继发性机械性痛觉过敏皮肤中的总和没有显著变化。高刺激强度下的时间总和比低刺激强度下更明显（P < 0.0002）。我们发现时间总和与继发性痛觉过敏区域之间、以及时间总和与热损伤诱发期间的疼痛强度之间均无相关性。我们得出结论，人类热损伤后原发性和继发性机械性痛觉过敏的发展与疼痛电刺激的时间总和变化无关。
