Pain Sensitization and Habituation in a Model of Experimentally-Induced Insomnia Symptoms

 描述(由申请人提供)：数量和质量良好的健康睡眠越来越被视为防止疼痛发展和/或加剧的保护因素。然而，睡眠不足，如失眠，在普通人群中越来越常见，并与慢性疼痛高度并存。虽然失眠的出现与疼痛症状的出现或恶化之间存在既定的关系，但这种关系背后的机制尚不清楚。这项提议的目的是研究失眠-疼痛方向性的两个潜在的可能机制：(1)炎症：当睡眠不足时，促炎标记物(白细胞介素6、前列腺素E_2)增加，抗炎标记物(分解素)减少，并有助于伤害性系统的敏化(即对疼痛信号的反应增加)。(2)疼痛抑制：当睡眠不足时，抑制疼痛的能力会恶化，从而阻止对疼痛的习惯性(对疼痛信号的反应降低)。疼痛抑制是控制传入疼痛信号的中心过程。这两个候选机制将在一个新的模型中进行测试，该模型重复暴露于实验诱导的失眠，其特征是(1)诱导典型的失眠症状(睡眠开始延迟、睡眠中断、清晨醒来)和(2)重复诱导这种模拟失眠事件，这允许研究许多生物系统的一个关键特征，即系统适应重复应激或挑战的能力，如疼痛。我们假设，反复暴露于失眠通过促进两个过程来增加对慢性疼痛的易感性：(1)通过逐渐增加炎症反应而使伤害性感受系统敏化；(2)通过逐渐恶化疼痛抑制反应来降低对疼痛的习惯性。26名健康的女性和男性将接受两次为期17天的内部平衡住院治疗(诱导失眠症状与控制睡眠状况)，其中将使用频繁的血液和尿液采样以及复杂的疼痛测试组合来调查以下情况 目的：目的1假设反复暴露于实验诱导的失眠症状时，炎症反应(IL-6、PGE2、解决素)逐渐增加，导致伤害性系统敏化，表现为对压力和高温的痛阈值降低，以及时间疼痛总和(中枢敏化的指标)增加。目的2假设疼痛抑制反应(由条件性疼痛调制测试测量)的渐进性恶化，导致对疼痛的较少习惯性。目的3假设炎症和疼痛抑制系统在反复暴露于实验诱导的失眠症状后恢复到基线的能力逐渐受损。这项研究对于未来针对特定机制预防或减轻因失眠而加剧的疼痛的新策略的开发是基础的。

 DESCRIPTION (provided by applicant): Healthy sleep of good quantity and quality is increasingly viewed as a protective factor against the development and/or exacerbation of pain. However, deficient sleep, such as insomnia, is increasingly common in the general population and is highly co-morbid with chronic pain conditions. Though there is an established relationship between the presence of insomnia and the onset or worsening of pain symptoms, the mechanisms underlying this relationship are unknown. The goal of this proposal is to investigate two promising mechanistic candidates underlying the insomia-to-pain directionality: (1) Inflammation: Pro-inflammatory markers (interleukin-6, prostaglandin E2) increase and anti- inflammatory markers (resolvins) decrease when sleep is deficient, and contribute to the sensitization of the nociceptive system (i.e., increased responsiveness to pain signals). (2) Pain inhibition: The capacity to inhibit pain, a central process to control incoming pain signals, is deteriorated when sleep is deficient, thus preventing habituation to pain (decreased responsivness to pain signals). These two mechanistic candidates will be tested in a novel model of repeated exposure to experimentally-induced insomnia, characterized by (1) induction of typical insomnia symptoms (delayed sleep onset, sleep disruption, early morning awakening) and (2) repeated induction of such simulated insomnia episodes, which allows for the investigation of a key feature of many biological systems, i.e. the ability of systems to adapt to repeated stressor or challenge, such as pain. We hypothezise that repeated exposure to insomnia increases vulnerability to chronic pain by promoting two processes: (1) sensitization of the nociceptive system via a progressive increase of the inflammatory response and (2) decreased habituation to pain via a progressive deterioration of the pain-inhibitory response. Twenty-six healthy women and men will undergo two intra-individual balanced 17- day in-hospital stays (insomnia symptoms induction vs control sleep condition), in which frequent blood and urine sampling and a complex pain testing battery will be utilized to investigate the following aims: Aim 1 postulates a progressive increase of the inflammatory response (IL-6, PGE2, resolvins) to repeated exposure to experimentally-induced insomnia symptoms, leading to sensitization of the nociceptive system as manifested by lower pain thresholds to pressure and heat, as well as increased temporal summation of pain (an index of central sensitization). Aim 2 postulates a progressive deterioration of the pain-inhibitory response (measured by the conditioned pain modulation test), contributing to less habituation to pain. Aim 3 postulates a progressive impairment of the ability of the inflammatory and pain-inhibitory system to return to baseline upon repeated exposure to experimentally-induced insomnia symptoms. This research is fundamental for the future development of novel strategies targeting specific mechanisms to prevent or reduce pain exacerbated by insomnia.