Drummond Peter D, Blockey Paul
School of Psychology, Murdoch University, Perth, Australia.
Somatosens Mot Res. 2009 Dec;26(4):75-81. doi: 10.3109/08990220903296761.
The aim of this study was to investigate tactile sensitivity near the site of primary hyperalgesia evoked by capsaicin applied topically to the dorsolateral aspect of the hand. In the first experiment (N = 15), touch thresholds increased in the fifth finger ipsilateral to the topically applied capsaicin, but remained unchanged at greater distances from the site of capsaicin treatment. In a second experiment (N = 12), the effect of the capsaicin treatment on sensations evoked not only by light touch but also by warmth, heat-pain, and pressure-pain to a 2-mm diameter steel probe was investigated in the fifth finger. Again, tactile sensitivity was inhibited at the fifth finger, even though stimulation with a cotton bud evoked no discomfort; moreover, sensitivity to warmth and heat-pain were unimpaired. However, sensitivity to pressure-pain increased in the fifth finger after the capsaicin treatment, possibly due to activation of nociceptors sandwiched between the probe tip and bone that normally responded to sharp stimuli. These findings suggest that the central mechanisms that mediate secondary mechanical hyperalgesia suppress sensitivity to innocuous tactile sensations. This effect may contribute to tactile hypoesthesia in chronic pain conditions.
本研究的目的是调查局部应用辣椒素于手背外侧诱发原发性痛觉过敏部位附近的触觉敏感性。在第一个实验（N = 15）中，局部应用辣椒素同侧的小指触觉阈值升高，但在距辣椒素治疗部位更远的距离处保持不变。在第二个实验（N = 12）中，研究了辣椒素治疗对用直径2毫米的钢探针进行轻触、温热、热痛和压痛所诱发感觉的影响，同样是在小指上进行。尽管用棉签刺激未引起不适，但小指的触觉敏感性仍受到抑制；此外，对温热和热痛的敏感性未受损害。然而，辣椒素治疗后小指对压痛的敏感性增加，这可能是由于夹在探针尖端和骨头之间的伤害感受器被激活，这些感受器通常对尖锐刺激有反应。这些发现表明，介导继发性机械性痛觉过敏的中枢机制会抑制对无害触觉感觉的敏感性。这种效应可能导致慢性疼痛状态下的触觉减退。
