Vase Lene, Robinson Michael E, Verne Nicholas G, Price Donald D
Department of Psychology, University of Aarhus, Aarhus, Denmark Department of Clinical and Health Psychology, University of Florida, HPNP, 101 S. Newell Dr. 3151, P.O. Box 100165, Gainesville, FL 32610-0165, USA Department of Gastroenterology, Veterans Administration Hospital, Gainesville, FL, USA Departments of Neuroscience and of Oral and Maxillofacial Surgery, University of Florida, Gainesville, FL, USA.
Pain. 2005 Jun;115(3):338-347. doi: 10.1016/j.pain.2005.03.014.
A study was conducted to determine whether changes in expected pain levels, desire for pain relief, or anxiety contribute to an increase in placebo analgesia over time as well as to determine whether placebo analgesic effects of IBS patients are related to endogenous opioid mechanisms. Twenty-six women with IBS were exposed to rectal stimulation (35 or 55 mmHg for 30 s) and tested under natural history (NH), rectal placebo (RP) and rectal lidocaine (RL) conditions. During all conditions, 16 patients were given saline intravenously (to test for a placebo effect) and 10 patients were given naloxone intravenously (to test naloxone antagonism of the placebo effect) on a double blind basis. Patients rated expected pain level, desire for pain relief and anxiety at 2 and 22 min after the onset of NH, RP, and RL conditions and they rated actual pain intensity at 5-min intervals for 40 min. There was a large and significant placebo effect (P<0.001) that increased over time. Ratings of expected pain levels, desire for pain relief and anxiety decreased over time and contributed to more variance in placebo and lidocaine responses during the last half of the session. These changes suggest that a reduction in negative emotions may be central to placebo effects. There was no significant difference between psychological mediators (desire, expectation, anxiety) or the placebo effect in the saline and naloxone groups, indicating that neither the psychological mediators nor the placebo analgesic effect were associated with endogenous opioids in this clinically related paradigm.
开展了一项研究，以确定预期疼痛水平的变化、缓解疼痛的愿望或焦虑是否会随着时间的推移导致安慰剂镇痛作用增强，以及确定肠易激综合征（IBS）患者的安慰剂镇痛效果是否与内源性阿片类机制有关。26名患有IBS的女性接受直肠刺激（35或55 mmHg，持续30秒），并在自然病程（NH）、直肠安慰剂（RP）和直肠利多卡因（RL）条件下进行测试。在所有条件下，16名患者静脉注射生理盐水（以测试安慰剂效应），10名患者静脉注射纳洛酮（以测试纳洛酮对安慰剂效应的拮抗作用），均采用双盲法。患者在NH、RP和RL条件开始后2分钟和22分钟时对预期疼痛水平、缓解疼痛的愿望和焦虑进行评分，并在40分钟内每隔5分钟对实际疼痛强度进行评分。存在显著的安慰剂效应（P<0.001），且随着时间的推移而增强。预期疼痛水平、缓解疼痛的愿望和焦虑的评分随时间下降，并在实验后半段对安慰剂和利多卡因反应的更多变异性产生影响。这些变化表明，负面情绪的减少可能是安慰剂效应的核心。生理盐水组和纳洛酮组在心理调节因素（愿望、期望、焦虑）或安慰剂效应方面没有显著差异，表明在这种临床相关范式中，心理调节因素和安慰剂镇痛效应均与内源性阿片类物质无关。
