Fust Jens, Lalouni Maria, Vadenmark Lundqvist Viktor, Wärnberg Emil, Jensen Karin B
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
Pain Rep. 2021 Mar 24;6(1):e914. doi: 10.1097/PR9.0000000000000914. eCollection 2021 Jan-Feb.
Offset analgesia (OA), a large reduction in pain after a brief increase in intensity of an otherwise stable painful stimulus, has been established by a large body of research. But the opposite effect, onset hyperalgesia (OH), a disproportional hyperalgesic response after a briefly decreased intensity of a painful stimulus, has only been investigated in one previous study.
The aim of this study was to induce OA and OH in healthy participants and explore the effects of different stimulus ranges (increase/decrease of temperature) on OA and OH.
A total of 62 participants were tested in 2 identical experiments. Offset analgesia and OH conditions included 2 different temperature deviations (±1°C/±2°C) from initial temperature and were compared with a constant temperature (control).
Offset analgesia was successfully elicited in OA in experiment 1, and in OA and OA in experiment 2. Results indicate a continuous stimulus-response relationship between the stimulus range and the resulting hypoalgesic response. Onset hyperalgesia was only elicited in OH in experiment 1. Exploratory analysis showed that the lack of OH response in experiment 2 could be explained by sex differences, and that OA and OH responses were only weakly correlated.
The asymmetry between pain responses after a brief temperature increase and decrease suggests that different mechanisms are involved in the pain responses to increasing and decreasing temperature. This asymmetry may also be explained by high temperatures in OA condition (+1°C/+2°C above baseline) that could be seen as salient "learning signals," which augment the response to following changes in temperature.
偏移性镇痛（OA），即在原本稳定的疼痛刺激强度短暂增加后疼痛大幅减轻，已被大量研究所证实。但相反的效应，即起始性痛觉过敏（OH），即在疼痛刺激强度短暂降低后出现不成比例的痛觉过敏反应，此前仅有一项研究进行过探讨。
本研究旨在使健康参与者产生OA和OH，并探究不同刺激范围（温度升高/降低）对OA和OH的影响。
共有62名参与者在2个相同的实验中接受测试。偏移性镇痛和OH条件包括与初始温度的2种不同温度偏差（±1°C/±2°C），并与恒温（对照）进行比较。
在实验1的OA中成功诱发了偏移性镇痛，在实验2的OA和OA中也成功诱发了偏移性镇痛。结果表明刺激范围与由此产生的痛觉减退反应之间存在连续的刺激 - 反应关系。仅在实验1的OH中诱发了起始性痛觉过敏。探索性分析表明，实验2中OH反应的缺失可由性别差异解释，且OA和OH反应仅呈弱相关。
短暂温度升高和降低后疼痛反应的不对称表明，对温度升高和降低的疼痛反应涉及不同机制。这种不对称也可能由OA条件下的高温（高于基线1°C/2°C）解释，其可被视为显著的“学习信号”，增强对随后温度变化的反应。
