Shortly after it became the first orphan G protein–coupled receptor successfully cloned, the eponymously named nociceptin opioid peptide/orphaninFQ receptor (NOPR) and its endogenous ligand (N/OFQ) were speculated to mediate behaviors beyond nociception (1). Given the high levels of expression of N/OFQ and NOPR in hypothalamic, limbic, and monoaminergic structures across the mammalian brain (2,3), focus quickly turned toward the investigation of how this novel opioidergic system regulated stress and affective behaviors, such as anxiety and depression. To date, much of what we know regarding the role of N/OFQ and NOPR in stress has come from experiments in laboratory rodents. Numerous studies have demonstrated that central administration of N/OFQ as well as small molecule agonists of NOPR produces an anxiolytic effect and reduces release of the primary stress hormone corticosterone (analogous to cortisol in humans). Further, global knockout of N/OFQ or antagonism of NOPR is sufficient to increase corticosterone and reduce adaptive responses to acute stressors. Finally, various acute stressors (e.g., social stress and restraint stress) increase the expression of both N/OFQ and NOPR across limbic regions. While these data are suggestive of an antistress effect of nociceptin signaling, it is worth noting that not all reports support this hypothesis [for a comprehensive review of stress/ anxiety–related N/OFQ and NOPR findings, see (4)] and that antagonism of NOPR appears to elicit an antidepressant-like, pro-motivating effect (3), indicating a more complex relationship between nociceptin signaling and emotional behavior. Numerous potential explanations for these inconsistent findings exist, some methodological (differences in species, stress exposure, and timing of behavioral and neurochemical measurements) and others biological (differential effects of stress on nociceptin signaling in discrete brain circuits). Given that preclinical research seeks to improve our understanding of how these systems are impacted in human disease and to harness this knowledge for therapeutic benefit, it is tempting to look for consistency in the human literature on the interplay between stress and N/OFQ signaling. Unfortunately, there is a dearth of studies in this area, mostly owing to the lack of sufficient tools to assess N/OFQ or NOPR in vivo in human subjects with high selectivity. Capitalizing on recent optimizations in the development of positron emission tomography (PET) radioligands with high affinity for NOPR (5), a single study has thus far examined this interaction. The authors demonstrate that NOPR radioligand binding is increased in women who recently experienced sexual trauma and that NOPR density was positively associated with posttraumatic stress disorder symptoms (6). However, it cannot be

中文翻译：

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伤害感受素信号传导在压力中的复杂作用：神经影像学的清晰度？


在成为第一个成功克隆的孤儿 G 蛋白偶联受体后不久，同名的伤害感受肽阿片肽/孤儿宁 FQ 受体 (NOPR) 及其内源性配体 (N/OFQ) 被推测可介导伤害感受以外的行为 (1)。鉴于 N/OFQ 和 NOPR 在哺乳动物大脑的下丘脑、边缘系统和单胺能结构中表达水平很高 (2,3)，焦点很快转向研究这种新型阿片类药物系统如何调节压力和情感行为，例如焦虑和抑郁。迄今为止，我们对 N/OFQ 和 NOPR 在压力中的作用的了解大部分来自于实验室啮齿动物的实验。大量研究表明，中枢施用 N/OFQ 以及 NOPR 小分子激动剂可产生抗焦虑作用，并减少主要应激激素皮质酮（类似于人类的皮质醇）的释放。此外，N/OFQ 的整体敲除或 NOPR 的拮抗足以增加皮质酮并减少对急性应激源的适应性反应。最后，各种急性压力源（例如社交压力和束缚压力）会增加边缘区域 N/OFQ 和 NOPR 的表达。虽然这些数据表明伤害感受素信号传导具有抗应激作用，但值得注意的是，并非所有报告都支持这一假设[有关压力/焦虑相关的 N/OFQ 和 NOPR 研究结果的全面回顾，请参阅 (4)]，并且拮抗作用NOPR 似乎会引发类似抗抑郁药的促激励作用 (3)，表明伤害感受素信号传导与情绪行为之间存在更复杂的关系。 对于这些不一致的发现存在许多潜在的解释，一些是方法论的（物种差异、压力暴露以及行为和神经化学测量的时间安排），另一些是生物学的（压力对离散脑回路中伤害感受素信号传导的不同影响）。鉴于临床前研究旨在提高我们对这些系统如何在人类疾病中受到影响的理解，并利用这些知识获得治疗益处，我们很容易在人类文献中寻找关于压力和 N/OFQ 信号传导之间相互作用的一致性。不幸的是，该领域的研究缺乏，主要是由于缺乏足够的工具来高选择性地评估人类受试者体内的 N/OFQ 或 NOPR。利用对 NOPR (5) 高亲和力的正电子发射断层扫描 (PET) 放射性配体开发的最新优化，迄今为止，一项研究已经检验了这种相互作用。作者证明，在最近经历过性创伤的女性中，NOPR 放射性配体结合增加，并且 NOPR 密度与创伤后应激障碍症状呈正相关 (6)。 然而，它不能