Sirucek Laura, Jutzeler Catherine Ruth, Rosner Jan, Schweinhardt Petra, Curt Armin, Kramer John Lawrence Kipling, Hubli Michèle
Spinal Cord Injury Center, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
Integrative Spinal Research Group, Department of Chiropractic Medicine, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
Pain Med. 2020 Nov 1;21(11):2839-2849. doi: 10.1093/pm/pnaa041.
Descending pain modulation can be experimentally assessed by way of testing conditioned pain modulation. The application of tonic heat as a test stimulus in such paradigms offers the possibility of observing dynamic pain responses, such as adaptation and temporal summation of pain. Here we investigated conditioned pain modulation effects on tonic heat employing participant-controlled temperature, an alternative tonic heat pain assessment. Changes in pain perception are thereby represented by temperature adjustments performed by the participant, uncoupling this approach from direct pain ratings. Participant-controlled temperature has emerged as a reliable and sex-independent measure of tonic heat.
Thirty healthy subjects underwent a sequential conditioned pain modulation paradigm, in which a cold water bath was applied as the conditioning stimulus and tonic heat as a test stimulus. Subjects were instructed to change the temperature of the thermode in response to variations in perception to tonic heat in order to maintain their initial rating over a two-minute period. Two additional test stimuli (i.e., lower limb noxious withdrawal reflex and pressure pain threshold) were included as positive controls for conditioned pain modulation effects.
Participant-controlled temperature revealed conditioned pain modulation effects on temporal summation of pain (P = 0.01). Increased noxious withdrawal reflex thresholds (P = 0.004) and pressure pain thresholds (P < 0.001) in response to conditioning also confirmed inhibitory conditioned pain modulation effects.
The measured interaction between conditioned pain modulation and temporal summation of pain supports the participant-controlled temperature approach as a promising method to explore dynamic inhibitory and facilitatory pain processes previously undetected by rating-based approaches.
下行性疼痛调制可通过测试条件性疼痛调制进行实验评估。在此类范式中，将持续性热刺激作为测试刺激应用，为观察动态疼痛反应（如疼痛适应和时间总和）提供了可能。我们在此研究了采用参与者控制温度（一种替代的持续性热痛评估方法）对持续性热刺激的条件性疼痛调制效果。疼痛感知的变化通过参与者进行的温度调节来体现，从而使该方法与直接疼痛评分脱钩。参与者控制温度已成为一种可靠且与性别无关的持续性热刺激测量方法。
30名健康受试者接受了序贯条件性疼痛调制范式，其中冷水浴作为条件刺激，持续性热刺激作为测试刺激。受试者被要求根据对持续性热刺激的感知变化来改变热刺激器的温度，以便在两分钟内保持其初始评分。另外纳入了两个测试刺激（即下肢有害性退缩反射和压力痛阈值）作为条件性疼痛调制效果的阳性对照。
参与者控制温度显示出对疼痛时间总和的条件性疼痛调制效果（P = 0.01）。条件刺激后有害性退缩反射阈值增加（P = 0.004）和压力痛阈值增加（P < 0.001）也证实了抑制性条件性疼痛调制效果。
所测量的条件性疼痛调制与疼痛时间总和之间的相互作用支持了参与者控制温度方法，认为这是一种有前景的方法，可用于探索基于评分的方法之前未发现的动态抑制性和易化性疼痛过程。
