Bitar Nathalie, Marchand Serge, Potvin Stéphane
Centre de recherche de l'Institut Universitaire en Santé Mentale de Montréal, Montreal, QC, Canada.
Department of Psychiatry, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada.
Pain Res Manag. 2018 Jun 3;2018:1935056. doi: 10.1155/2018/1935056. eCollection 2018.
Inhibitory conditioned pain modulation (ICPM) is one of the principal endogenous pain inhibition mechanisms and is triggered by strong nociceptive stimuli. Recently, it has been shown that feelings of pleasantness are experienced after the interruption of noxious stimuli. Given that pleasant stimuli have analgesic effects, it is therefore possible that the ICPM effect is explained by the confounding effect of pleasant pain relief. The current study sought to verify this assumption.
Twenty-seven healthy volunteers were recruited. Thermal pain thresholds were measured using a Peltier thermode. ICPM was then measured by administering a tonic thermal stimulus before and after a cold-pressor test (CPT). Following the readministration of the CPT, pleasant pain relief was measured for 4 minutes. According to the opponent process theory, pleasant relief should be elicited following the interruption of a noxious stimulus.
The interruption of the CPT induced a and pleasant pain relief of almost 40% and 70%, respectively. Pleasant pain relief did not correlate with ICPM amplitude but was positively correlated with pain level during the CPT. Finally, a negative correlation was observed between pleasant pain relief and anxiety.
Results show that the cessation of a strong nociceptive stimulus elicits potent pleasant pain relief. The lack of correlation between ICPM and pleasant pain relief suggests that the ICPM effect, as measured by sequential paradigms, is unlikely to be fully explained by a pleasant pain relief phenomenon.
抑制性条件性疼痛调制（ICPM）是主要的内源性疼痛抑制机制之一，由强烈的伤害性刺激触发。最近的研究表明，在有害刺激中断后会产生愉悦感。鉴于愉悦刺激具有镇痛作用，因此ICPM效应有可能是由愉悦性疼痛缓解的混杂效应所解释。本研究旨在验证这一假设。
招募了27名健康志愿者。使用珀耳帖热刺激器测量热痛阈值。然后在冷加压试验（CPT）前后通过给予持续性热刺激来测量ICPM。在再次进行CPT后，测量4分钟内的愉悦性疼痛缓解情况。根据对手过程理论，有害刺激中断后应引发愉悦性缓解。
CPT的中断分别诱导了近40%和70%的愉悦性疼痛缓解。愉悦性疼痛缓解与ICPM幅度无关，但与CPT期间的疼痛程度呈正相关。最后，观察到愉悦性疼痛缓解与焦虑之间存在负相关。
结果表明，强烈伤害性刺激的停止会引发强烈的愉悦性疼痛缓解。ICPM与愉悦性疼痛缓解之间缺乏相关性表明，通过顺序范式测量的ICPM效应不太可能完全由愉悦性疼痛缓解现象来解释。
