电针缓解慢性炎性肠病内脏痛及继发躯体痛敏的机制研究

Visceral pain, as a main symptom of chronic inflammatory bowel disease, is often associated with somatic secondary hyperalgesia (referred pain) and autonomic dysfunctions. It has showed that abnormal expressions of SP, CGRP and NMDA receptors in spinal dorsal horn mediate the generation of hyperalgsia under somatic chronic pain condition via inducing long-term potentiation (LTP) of synaptic plasticity in spinal noxious signaling pathway. In fact, similar abnormal expressions of those aforementioned neurotransmitters and receptors have been found in the spinal dorsal horn under chronic inflammatory bowel disease condition. In addition, somatic secondary hyperalgesia can be elicited by long-lasting visceral pain. Therefore, we are more likely to speculate that the facilitated spinal LTP is also existed under chronic inflammatory bowel disease condition. It has shown that electro-acupuncture is effective to relief pain via modulating the activity of pain related neurons and the expression of some bioactive molecules in central nerve system. With respect to changes of synaptic plasticity in spinal noxious signaling pathway, the therapeutic effects of electro-acupuncture at ST36 on visceral pain and somatic secondary hyperalgesia in chronic inflammatory bowel disease model rats will be investigated in the proposed study, by means of behavioral test, extracellular electrophysiological recording with multiple channels micro-electrode arrays and molecular biological techniques. Additionally, the impact of electro-acupuncture on the spinal LPT and its molecular basis will be studied to explore the neurobiological mechanism underlying electro-acupuncture induced anti-hyperalgesia effects.

内脏痛是慢性炎性肠病的主要临床表现之一，常可引起继发性躯体痛敏（牵涉痛）和植物神经活动紊乱等症状。慢性躯体痛时脊髓背角SP、CGRP及NMDA受体的异常表达可通过易化脊髓背角伤害性神经元突触传递的长时程增强（LTP）介导痛觉过敏。在慢性炎性肠病模型动物的脊髓背角，上述神经递质和受体也存在类似的表达异常；而且持续性的内脏痛常会引起继发性躯体痛敏。因此，我们推测在慢性炎性肠病状态下，脊髓痛觉信息突触传递的LTP也可能存在着易化。已知电针可通过影响中枢痛相关神经元的活动和某些活性物质的表达来缓解疼痛。本课题以伤害性信息突触传递的可塑性变化为切入点，拟采用行为学、多通道微电极阵列记录及分子生物学等方法，观察长期电针足三里对慢性炎性肠病模型大鼠内脏痛及继发躯体痛敏的影响；探讨电针对脊髓伤害性信息突触传递可塑性的影响及其分子基础，揭示脊髓背角水平电针缓解痛觉过敏的神经生物学机制。

以往研究表明，肠易激综合征患者和结肠炎模型大鼠除了内脏痛敏的表现外，还可伴有继发性的躯体痛敏/牵涉痛，但其神经机制尚不明确。已知脊髓背角突触传递的长时程增强（LTP）现象在躯体慢性痛痛觉过敏的形成过程中发挥重要的作用，本研究旨在揭示脊髓LTP在结肠炎引起继发躯体痛敏中的作用，并进一步观察电针是否能够通过抑制脊髓LTP从而缓解继发性躯体痛敏。采用2, 4, 6三硝基苯磺酸（TNBS）结肠灌注建立大鼠结肠炎模型，通过结直肠扩（CRD）张诱发内脏运动反射（VMR）作为内脏高敏感指标，利用von Frey纤维丝和辐射热刺激仪分别测定大鼠双侧足底机械和热痛感觉异常，以高频率高强度电刺激坐骨神经诱发L4-L6脊髓背角C纤维诱发场电位（CFEFP）和LTP情况。结果表明：TNBS模型组大鼠末端结肠出现明显的炎性病变，CRD诱发VMR反射显著增强，同时其双侧足底机械和热痛反射潜伏期明显缩短，提示出现继发性躯体痛敏。电针足三里和上巨虚可以减缓结肠局部炎症、内脏痛敏和继发性躯体痛敏。值得注意的是，电针还可以降低TNBS模型组大鼠诱发CFEFP的阈值和脊髓LTP易化程度。综上，本研究结果提示TNBS诱发结肠炎大鼠可同时出现内脏痛敏和继发性躯体痛敏，后者可能与脊髓背角伤害性信息突触传递可塑性的增强，即LTP易化相关。电针足三里和上巨虚可通过抑制脊髓LTP缓解内脏炎症引起的结肠痛敏和继发性躯体痛敏。