Centre for Neuroscience Studies, Queen's University, Kingston, ON, Canada.
Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada.
Pain. 2018 Oct;159(10):2012-2020. doi: 10.1097/j.pain.0000000000001302.
Descending regulation of spinal cord responses to nociceptive signaling has a strong influence on pain perception. Previous studies using functional magnetic resonance imaging (fMRI) have indicated that in addition to reactive responses to nociceptive signals, there is a continuous component to regulation, and that it may vary with differences in pain sensitivity. We hypothesize that this continuous regulation component occurs routinely in fMRI studies before noxious stimulation, as well as during, and after stimulation. This hypothesis was tested by analyzing data from 59 healthy participants in 4 previous fMRI studies in our laboratory using noxious heat stimuli. Analyses included structural equation modeling to identify coordinated blood oxygenation-level-dependent (BOLD) signal variations between regions (ie, connectivity) and Bayesian regression of BOLD time-series responses in relation to pain ratings and stimulus temperatures. The results demonstrate the periaqueductal gray-rostral ventromedial medulla-spinal cord descending modulation pathway, influenced by input from the hypothalamus, parabrachial nucleus, and nucleus tractus solitarius. Connectivity between specific regions is observed to vary in relation to pain sensitivity. The results support the conclusion that homeostatic autonomic control influences the net descending pain regulation, and therefore influences pain sensitivity. The results describe the overall properties of pain processing (specifically pain elicited by heat) in the healthy human brainstem and spinal cord, and mechanisms for variation across individuals. This understanding is expected to be important for studies of how pain processing is altered in chronic pain conditions.
脊髓对伤害性信号的反应的下行调节对疼痛感知有很强的影响。先前使用功能磁共振成像（fMRI）的研究表明，除了对伤害性信号的反应性调节外，还有一个连续的调节成分，并且它可能因疼痛敏感性的差异而有所不同。我们假设这种连续的调节成分在 fMRI 研究中在有害刺激之前、期间和之后都会常规发生。通过分析我们实验室之前的 4 项 fMRI 研究中 59 名健康参与者的数据，对该假设进行了测试，这些研究使用了有害热刺激。分析包括结构方程建模，以识别区域之间（即连通性）的血氧水平依赖（BOLD）信号变化的协调性，以及 BOLD 时间序列响应与疼痛评分和刺激温度之间的贝叶斯回归。结果表明，由下丘脑、脑桥臂旁核和孤束核输入影响的导水管周围灰质-吻侧腹内侧髓质-脊髓下行调制通路。观察到特定区域之间的连通性与疼痛敏感性有关。结果支持这样的结论，即自主平衡控制影响下行疼痛调节的净效应，因此影响疼痛敏感性。结果描述了健康人脑干和脊髓中疼痛处理（特别是热引起的疼痛）的整体特性，以及个体间差异的机制。这种理解对于研究慢性疼痛条件下疼痛处理如何改变的研究预计将非常重要。
