Wong Felyx, Reddy Aditi, Rho Yeanuk, Vollert Jan, Strutton Paul H, Hughes Sam W
The Nick Davey Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom.
Pain Research, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom.
Pain Rep. 2023 Apr 4;8(3):e1071. doi: 10.1097/PR9.0000000000001071. eCollection 2023 May-Jun.
Topical application of capsaicin can produce an ongoing pain state in healthy participants. However, approximately one-third report no pain response (ie, nonresponders), and the reasons for this are poorly understood.
In this study, we investigated temporal summation of pain (TSP) profiles, pain ratings and secondary hyperalgesia responses in responders and nonresponders to 1% topical capsaicin cream.
Assessments were made at baseline and then during an early (ie, 15 minutes) and late (ie, 45 minutes) time points post-capsaicin in 37 healthy participants.
Participants reporting a visual analogue scale (VAS) rating of >50 were defined as responders (n = 24) and those with <50 VAS rating were defined as nonresponders (n = 13). There was a facilitation of TSP during the transition from an early to the late time point post-capsaicin (P<0.001) and the development of secondary hyperalgesia (P<0.05) in the responder group. Nonresponders showed no changes in TSP or secondary hyperalgesia during the early and late time points. There was an association between baseline TSP scores and the later development of a responder or nonresponder phenotype (r = 0.36; P = 0.03). Receiver operating characteristic analysis revealed that baseline TSP works as a good response predictor at an individual level (area under the curve = 0.75).
These data suggest that responders and nonresponders have different facilitatory pain mechanisms. The assessment of TSP may help to identify participants with stronger endogenous pain facilitation who may be more likely to respond to topical capsaicin.
辣椒素局部应用可使健康受试者产生持续性疼痛状态。然而，约三分之一的受试者报告无疼痛反应（即无反应者），其原因尚不清楚。
在本研究中，我们调查了对1%局部辣椒素乳膏有反应者和无反应者的疼痛时间总和（TSP）特征、疼痛评分及继发性痛觉过敏反应。
对37名健康受试者在基线时进行评估，然后在辣椒素应用后的早期（即15分钟）和晚期（即45分钟）时间点进行评估。
视觉模拟量表（VAS）评分>50的受试者被定义为有反应者（n = 24），VAS评分<50的受试者被定义为无反应者（n = 13）。在辣椒素应用后从早期到晚期的时间点过渡期间，有反应者组的TSP增强（P<0.001），继发性痛觉过敏出现（P<0.05）。无反应者在早期和晚期时间点的TSP或继发性痛觉过敏无变化。基线TSP评分与随后出现的有反应者或无反应者表型之间存在关联（r = 0.36；P = 0.03）。受试者工作特征分析显示，基线TSP在个体水平上是一个良好的反应预测指标（曲线下面积 = 0.75）。
这些数据表明，有反应者和无反应者具有不同的疼痛易化机制。TSP评估可能有助于识别内源性疼痛易化较强、可能更易对局部辣椒素产生反应的受试者。
