Spinal AMPA receptors, latent central sensitization and chronic pain

描述(由申请人提供)：迫切需要进行研究，以更好地了解调节从急性疼痛到慢性疼痛的中枢神经系统机制。医学研究所表示，1.16亿美国人背负着慢性疼痛的负担，每年花费超过6000亿美元。虽然阿片类药物通常用于治疗疼痛，但它们只有适度的疗效，副作用和滥用的可能性强调了更多了解其止痛机制的必要性。大量研究表明，外周炎症启动了脊髓和大脑内的非适应性可塑性，称为中枢敏感化--从而导致慢性疼痛。然而，不太受重视的是，有数据表明，中枢敏感化的持续时间远远超过疼痛敏感的显性迹象，这种无声的形式被称为“潜伏性中枢 敏化“(LCS)。这一建议是创新的，因为它提出了一种新的LCS的分子机制；中心假设是炎症产生依赖于腺苷环化酶1(AC1)和AMPA受体(AMPAR)的LCS，该依赖于脊髓阿片受体。这一假说将通过三个特定的目的进行检验：目的1检验强直的MU阿片受体(MOR)活性降低损伤后长时间LCS中AMPAR介导的背角钙信号的假说。目的1在成年脊髓背角脑片上应用实时钙成像技术，研究阿片受体阻断剂是否增加AMPAR介导的脊髓背角钙信号传导。目的2验证AMPAR亚基GluA2磷酸化和内化维持LCS的假说。Aim 2将通过测量在NTX存在或不存在的情况下GluA2 Ser880的磷酸化和内化来验证这一假说。目的3验证损伤诱导的GluA2内化和钙通透性的长期增加是由AC1活性维持的假说。在AC1缺失或药物抑制的小鼠的DH中，Aim 3将比较AMPAR介导的钙反应，并在存在或不存在阿片受体阻断的情况下确定总的和磷酸化的GluA2和细胞表面的表达。这项拟议的研究意义重大，因为如果我们的假设是正确的，那么任何干扰阿片受体活性的事件都可能释放前伤害性AC1-AMPAR信号，从而允许过渡到慢性疼痛。这一提议中产生的结果和概念可能导致我们对组织炎症后疼痛易感性的理解的垂直飞跃，并具有揭示新靶点的长期潜力 防止从急性疼痛向慢性疼痛的过渡。

DESCRIPTION (provided by applicant): There is an overwhelming need for research leading to a greater understanding of central nervous system mechanisms that regulate the transition from acute to chronic pain. The Institute of Medicine states that 116 million Americans are burdened with chronic pain, costing over $600 billion annually. While opioid medications are commonly prescribed to treat pain, they are only moderately efficacious, and adverse side effects and potential for abuse stress the need for greater understanding of their analgesic mechanisms. A large body of research indicates that peripheral inflammation initiates maladaptive plasticity within the spinal cord and brain, termed central sensitization-that contributes to chronic pain. Less appreciated, however, are data which suggest that central sensitization far outlasts overt signs of pain sensitivity, in a silent form termed "latent central sensitization" (LCS). This proposal is innovative in that it suggests a novel molecular mechanism of LCS; the central hypothesis is that inflammation produces an adenylyl cyclase 1 (AC1)- and AMPA receptor (AMPAR)-dependent LCS that is masked by spinal opioid receptors. This hypothesis will be tested with three specific aims: AIM 1 tests the hypothesis that tonic mu opioid receptor (MOR) activity decreases dorsal horn AMPAR-mediated Ca2+ signaling during long-lasting LCS after injury. Aim 1 uses innovative real-time Ca2+ imaging in adult spinal dorsal horn (DH) slices to determine whether opioid receptor blockade increases AMPAR-mediated DH Ca2+ signaling. AIM 2 tests the hypothesis that AMPAR subunit GluA2 phosphorylation and internalization maintains LCS. Aim 2 will test this hypothesis by measuring GluA2 Ser880 phosphorylation and internalization in the presence or absence of NTX. AIM 3 tests the hypothesis that injury-induced long- term increases in GluA2 internalization and Ca2+ permeability are maintained by AC1 activity. In DH from mice with AC1 deletion or pharmacological inhibition, Aim 3 will compare AMPAR-mediated Ca2+ responses and determine total and phosphorylated GluA2 and cell surface expression in the presence or absence of opioid receptor blockade. The proposed research is significant because if our hypotheses are correct, then any event that interferes with opioid receptor activity could unleash pronociceptive AC1-AMPAR signaling, and thus allow the transition to chronic pain. The results and concepts generated in this proposal may lead to a vertical leap in our understanding of pain vulnerability after tissue inflammation, and has the long-term potential to reveal novel targets to prevent the transition from acute to chronic pain.