Oono Yuka, Nie Hongling, Matos Renata Lima, Wang Kelun, Arendt-Nielsen Lars
Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7, Bld. D3, DK-9220 Aalborg E, Aalborg, Denmark.
Department of Oral & Maxillofacial Surgery, Aalborg Hospital, Aalborg, Denmark.
Scand J Pain. 2011 Oct 1;2(4):162-169. doi: 10.1016/j.sjpain.2011.05.006.
Background and purpose Conditioned pain modulation (CPM) is a phenomenon in which pain is inhibited by heterotopic noxious stimulation. It is not known how the experimental condition affects the magnitude of the CPM response and the inter-and intra-individual variations. It is important to get the information of the test-retest reliability and inter-individual variations of CPM to apply CPM as a diagnostic tool or for screening analgesic compounds. This study evaluated (1) the magnitude of CPM, (2) the inter-individual coefficient of variation (inter-CV) and (3) the intra-individual coefficient of variation (intra-CV) to (A) different stimulus modalities to evoke CPM and (B) different assessment sites. Methods Twelve healthy men (age 19-38 years) participated in this study. Cold pressor pain (CPP) (immersing the hand into cold water), tourniquet pain (cuff around the upper arm) and mechanical pressure pain (craniofacial region) were used in randomized order as conditioning stimuli (CS). The test stimulus (TS) was pressure pain applied to the right masseter muscle, left forearm and leg (bilateral tibialis anterior: TA). The responses were pressure pain thresholds (PPT), pressure pain tolerance (PPTol) thresholds and the pain intensity which was assessed on a visual analogue scale (VAS, 0-10 cm) following 1.4 and 1.6 × PPT applied to TA. The TS was applied before, during and 10 min after the CS. The intra-individual CV was estimated between different days. Results CPP induced the most powerful CPM on PPT (66.3 ± 10.0% increase), VAS ratings (41.5 ± 5.3% reduction) and PPTol (32.6±4.6% increase), especially at TA, and resulted in the smallest inter-CV (41.4-60.1%). Independently of the CS, the inter-CV in general showed that the recordings from the orofacial region and the forearm had smaller values than from the leg. The smallest intra-CV value was obtained in pain ratings with CPP (27.0%). Conclusions This study suggests that (1) the CPP evokes the largest CPM, (2) the leg as the assessment site results in the largest CPM responses and (3) the CPP causes the smallest inter- and intra-CV. Implication The present investigation implicates that the CPP is the most efficient conditioning stimulus to induce CPM when assessed by pressure pain thresholds.
背景与目的 条件性疼痛调制（CPM）是一种通过异位有害刺激抑制疼痛的现象。目前尚不清楚实验条件如何影响CPM反应的幅度以及个体间和个体内的差异。获取CPM的重测信度和个体间差异信息对于将CPM用作诊断工具或筛选镇痛化合物非常重要。本研究评估了（1）CPM的幅度，（2）个体间变异系数（inter-CV）和（3）个体内变异系数（intra-CV），以研究（A）诱发CPM的不同刺激方式和（B）不同评估部位的影响。方法 12名健康男性（年龄19 - 38岁）参与了本研究。冷加压疼痛（CPP）（将手浸入冷水中）、止血带疼痛（上臂扎袖带）和机械性压痛（颅面部区域）以随机顺序用作条件刺激（CS）。测试刺激（TS）为施加于右侧咬肌、左前臂和腿部（双侧胫骨前肌：TA）的压痛。反应指标为压痛阈值（PPT）、压痛耐受（PPTol）阈值以及在对TA施加1.4倍和1.6倍PPT后通过视觉模拟量表（VAS，0 - 10 cm）评估的疼痛强度。TS在CS之前、期间和之后10分钟施加。个体内CV在不同日期之间进行估计。结果 CPP在PPT（增加66.3±10.0%）、VAS评分（降低41.5±5.3%）和PPTol（增加32.6±4.6%）方面诱导出最强的CPM，尤其是在TA部位，并且导致最小的个体间CV（41.4 - 60.1%）。与CS无关，个体间CV总体显示，来自口面部区域和前臂的记录值比来自腿部的小。CPP在疼痛评分中获得最小的个体内CV值（27.0%）。结论 本研究表明：（1）CPP诱发的CPM最大；（2）腿部作为评估部位时CPM反应最大；（3）CPP导致最小的个体间和个体内CV。意义 本研究表明，当通过压痛阈值评估时，CPP是诱导CPM最有效的条件刺激。
