Long-term activation of spinal opioid analgesia after imflammation - Supplement

严重的组织损伤引起中枢敏化(中枢伤害性神经元对 正常或阈值以下的传入输入)，导致痛觉过敏。潜敏化(LS)是一种无声的 中枢敏感化的形式，在组织愈合和明显的痛觉过敏症状消失后仍然存在。 可以用阿片受体拮抗剂或反向激动剂“重新点燃”或恢复状态来揭示LS 痛觉过敏。因此，LS期间的疼痛缓解可能是通过掩饰紧张性阿片受体活性来维持的 LS的前伤害性成分。LS之所以重要，是因为它启动了伤害性感受系统，当 抑制系统失效，疼痛发作随之而来。理解LS的关键第一步是演示 翻译意义，我们现在证明阿片受体反向激动剂纳洛酮可以恢复 在一级继发性痛觉过敏症状解决后1周出现实验性疼痛 烫伤。特定目标1验证烧伤或手术触发LS和长期阿片类药物的假设 对人类的止痛作用。为了进一步研究LS的神经生物学机制，我们还将使用小鼠模型 这是持久的、强大的、广泛的、可重复的，并转化为人类研究。我们发现Mu 阿片受体(MOR)反向激动剂恢复痛觉过敏的行为和分子迹象，即使在 在组织损伤后几个月给药，这需要腺酰环化酶1型的NMDA受体激活 (AC1)。我们的结果很重要，因为它们表明，任何干扰MOR的事件，如压力，都会 在人类慢性疼痛综合征中，LS期间的镇痛会导致痛敏症状的复发。具体目标2 检验MOR结构性活动(MORCA)和/或MOR、增量(DOR)或kappa激活的假设 延髓轮状腹内侧区阿片肽(KOR)受体维持内源性镇痛 从而将LS限制在疼痛缓解的状态。具体目标3决定了MORS的程度 抑制双侧丘脑的空间协调神经活动(使用创新的通道场记录系统) 初级传入伤害性感受器的突触前终末或DH神经元上的突触强度(使用贴片 钳夹电生理学)。然后，特定目标4测试MORS是否特异性地抑制脊髓NMDA 受体亚单位(GluN2A或GluN2B)和/或Epac1(最近由cAMP直接激活的交换蛋白 被发现有助于外周疼痛感觉)，以在LS期间阻断疼痛。这个项目的完成将带来 我们更接近我们缓解慢性疼痛的长期目标，方法是：a)促进内源性阿片类止痛， 从而将LS限制在缓解状态内；或b)例如通过选择性的 AC1或Epac1抑制剂。我们的一般模型和假设与异种作用的概念有相似之处： 病理性地提高了相互促进的相反过程(MOR和LS)之间的平衡 相互反馈。我们的长期愿景是慢性疼痛治疗的新概念战略，以恢复 动态平衡，既没有中枢敏化，也没有MOR代偿反应。

Severe tissue injury generates central sensitization (increased responsiveness of CNS nociceptive neurons to normal or sub-threshold afferent input) that contributes to hyperalgesia. Latent sensitization (LS) is a silent form of central sensitization that persists after tissue has healed and overt signs of hyperalgesia have resolved. LS can be revealed with opioid receptor antagonists or inverse agonists that “rekindle” or reinstate hyperalgesia. Thus, pain remission during LS is likely maintained by tonic opioid receptor activity that masks the pronociceptive components of LS. LS is important because it primes nociceptive systems such that, when inhibitory systems fail, a pain episode ensues. A key first step in understanding LS is to demonstrate the translational significance, and we now show that the opioid receptor inverse agonist, naloxone, can reinstate experimental pain when delivered 1 wk after the resolution of secondary hyperalgesia following first degree thermal injury. Specific Aim 1 tests the hypothesis that burn or surgery triggers LS and long-term opioid analgesia in humans. To further study the neurobiological mechanisms of LS, we will also use a mouse model that is long-lasting, powerful, broad range, repeatable, and translates to human studies. We found that mu opioid receptor (MOR) inverse agonists reinstated behavioral and molecular signs of hyperalgesia, even when administered months after tissue injury, and this required NMDA receptor activation of adenylyl cyclase type 1 (AC1). Our results are important because they suggest that any event, such as stress, that interferes with MOR analgesia during LS will lead to relapse of hyperalgesia in chronic pain syndromes in humans. Specific Aim 2 tests the hypothesis that MOR constitutive activity (MORCA) and/or activation of MOR, delta (DOR), or kappa (KOR) receptors by opioid peptides in the DH or rostroventromedial medulla maintains endogenous analgesia and thereby restricts LS to a state of pain remission. Specific Aim 3 determines the extent to which MORs inhibit spatially coordinated neural activity in the DH (using an innovative 64-channel field recording system) and synaptic strength in presynaptic terminals of primary afferent nociceptors or on DH neurons (using patch clamp electrophysiology) during LS. Specific Aim 4 then tests whether MORs specifically inhibit spinal NMDA receptor subunits (GluN2A or GluN2B) and/or Epac1 (exchange protein directly activated by cAMP, recently found to contribute to peripheral pain senstization) to block pain during LS. Completion of this project will bring us closer to our long-term goal of alleviating chronic pain by either: a) facilitating endogenous opioid analgesia, thus restricting LS within a state of remission; or b) extinguishing LS altogether, for example with a selective AC1 or Epac1 inhibitor. Our general model and hypothesis shares similarities with the concept of allostasis: a pathologically-elevated balance between opposing processes (MOR and LS) that facilitate each other by mutual feedback. Our long-term vision is a new conceptual strategy for chronic pain therapy, to restore homeostasis, where there is neither central sensitization nor MOR compensatory responses.