BACKGROUND Acupuncture is used to reduce chronic musculoskeletal pain. The common mechanism underlying these types of pain are peripheral and/or central sensitization. In the clinical setting, it is difficult to separate the peripheral from the central component of pain. Heat/capsaicin 45°C/0.075%-induced hyperalgesia provides a stable, human central sensitization model in which the peripheral component is also assessed. AIM This randomized, sham-controlled study aimed to investigate the effect of electroacupuncture (EA) on the severity of heat (peripheral sensitization) and mechanical hyperalgesia (central sensitization) in a heat/capsaicin pain model in humans. METHODS Twenty-six healthy young participants (24 ± 3.9 years) were recruited. After baseline assessment, heat/capsaicin 45°C/0.075% was applied to the non-dominant forearm to induce hyperalgesia. The primary outcome measures were the size of the area of mechanical hyperalgesia, intensity of pain to heat stimulation and heat pain thresholds. The intensity of pain was recorded using modified 10-cm visual analogues scales (VAS). Participants were assessed at 70 min after the initial application of capsaicin then randomly allocated to receive either real electroacupuncture (REA, n = 14) or sham non-invasive EA (SEA, n = 12) for 30 min. The main outcome measures were assessed again immediately and then 90 min following EA. Credibility of blinding was assessed. Data were analyzed with t-tests or analysis of variance (ANOVA) where appropriate. RESULTS After the model was established, the area of mechanical hyperalgesia was formed (55.64 cm2), as was heat hyperalgesia, as the rating to heat stimulation, increased from 2/10 to 6/10. The REA and SEA groups were comparable. Immediately after the allocated acupuncture treatment, the rating to heat stimulation was statistically significantly lower in the REA group (2.94 ± 1.64) than in the SEA group (4.62 ± 2.26) (p < 0.05). The area of mechanical hyperalgesia reduced significantly without any group difference. No group difference was detected in heat pain threshold. Blinding of the participants was successful. CONCLUSION Peripheral and central sensitization in the heat/capsaicin 45°C/0.075% model responded to EA differently, suggesting that acupuncture analgesia could vary, depending on the types of pain. This observation may explain some inconsistent findings from clinical trials of acupuncture.

中文翻译：

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电针对人类外周和中枢敏化有不同的影响吗：一项随机对照研究。

背景技术针灸用于减轻慢性肌肉骨骼疼痛。这些类型疼痛的共同机制是外周和/或中枢敏化。在临床环境中，很难将疼痛的外周成分与中枢成分分开。热/辣椒素 45°C/0.075% 诱导的痛觉过敏提供了一种稳定的人体中枢敏化模型，其中还评估了外周成分。目的 本随机、假对照研究旨在调查电针 (EA) 对人体热/辣椒素疼痛模型中热（外周致敏）和机械痛觉过敏（中枢致敏）严重程度的影响。方法 招募了 26 名健康的年轻参与者（24 ± 3.9 岁）。基线评估后，加热/辣椒素 45°C/0。075% 应用于非优势前臂以诱导痛觉过敏。主要结果测量是机械痛觉过敏区域的大小、热刺激的疼痛强度和热痛阈值。使用改良的 10 厘米视觉模拟量表 (VAS) 记录疼痛的强度。参与者在最初应用辣椒素后 70 分钟接受评估，然后随机分配接受真正的电针（REA，n = 14）或假无创电针（SEA，n = 12）30 分钟。立即再次评估主要结果测量，然后在 EA 后 90 分钟进行评估。评估了盲法的可信度。在适当的情况下，用 t 检验或方差分析 (ANOVA) 分析数据。结果 模型建立后，形成机械性痛觉过敏区（55.64 cm2），热痛觉过敏区，作为对热刺激的评级，从 2/10 增加到 6/10。REA 和 SEA 组具有可比性。在分配针灸治疗后，REA 组 (2.94 ± 1.64) 的热刺激评分在统计学上显着低于 SEA 组 (4.62 ± 2.26) (p < 0.05)。机械性痛觉过敏面积显着减少，无组间差异。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。REA 和 SEA 组具有可比性。在分配针灸治疗后，REA 组 (2.94 ± 1.64) 的热刺激评分在统计学上显着低于 SEA 组 (4.62 ± 2.26) (p < 0.05)。机械性痛觉过敏面积显着减少，无组间差异。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。REA 和 SEA 组具有可比性。在分配针灸治疗后，REA 组 (2.94 ± 1.64) 的热刺激评分在统计学上显着低于 SEA 组 (4.62 ± 2.26) (p < 0.05)。机械性痛觉过敏面积显着减少，无组间差异。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。REA 组的热刺激评分 (2.94 ± 1.64) 在统计学上显着低于 SEA 组 (4.62 ± 2.26) (p < 0.05)。机械性痛觉过敏面积显着减少，无组间差异。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。REA 组的热刺激评分 (2.94 ± 1.64) 在统计学上显着低于 SEA 组 (4.62 ± 2.26) (p < 0.05)。机械性痛觉过敏面积显着减少，无组间差异。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。热痛阈值未检测到组间差异。参与者的盲法是成功的。结论 热/辣椒素 45°C/0.075% 模型中的外周和中枢敏化对 EA 的反应不同，表明针刺镇痛可能因疼痛类型而异。这一观察结果可以解释针灸临床试验中一些不一致的发现。