基于下行抑制系统及皮层可塑性探讨枕神经电刺激治疗偏头痛的作用机制研究

Pharmaceutical treatment of migraine may lead to side effect and poor compliance. In recent years, it has been studied that transcutaneous electrical nerve stimulation could be considered as an effective and safe non-drug treatment for migraine. A randomized controlled trial has been conducted to confirm the efficacy and tolerability of transcutaneous occipital nerve stimulation (ONS) in patients with migraine, however, its central underlying mechanism in treatment of migraine is still unclear. Based on the clinical study, animal experiments have been designed to further explore the mechanism of ONS in migraine by invasive and non-invasive ONS intervention. Endogenous descending inhibitory system is the key part in the modulation of migraine, and recent evidences suggest that the synaptic long-term potentiation (LTP) in anterior cingulate cortex (ACC) may play an important role in the regulation of chronic migraine. But it was unclear that whether ONS paly the treatment role in migraine by activating the descending inhibitory system and effecting cortical synaptic plasticity. In order to evaluate the underlying mechanism of ONS in migraine, the chronic migraine animal model will be firstly established to observe the changes of behaviors as well as the mechanism threshold before and after the invasive and noninvasive ONS. Next, the activation condition of pain modulation pathway will be observed by histochemical methods, and the release of endogenous neuropeptide will be evaluated by molecular biological technique. Finally, the electrophysiological technology including whole-cell patch clamp and multichannel field potential recording system will be used to observe the effect of ONS on synaptic LTP and to study synaptic plasticity in ACC as well. The results of this study could lay the foundations for ONS therapy of migraine and provide the theoretical basis for the further achievements of non-drug treatment in chronic migraine.

由于偏头痛治疗药物副作用大，患者接受程度不高，经皮神经电刺激作为安全有效的非药物治疗手段近年来逐渐受到关注。前期开展的随机对照临床研究已经明确了经皮枕神经电刺激(ONS)治疗偏头痛的有效性及安全性，但具体机制不明。本课题在此基础上设计动物实验通过有创及无创ONS干预偏头痛大鼠模拟临床治疗，进一步探索ONS治疗偏头痛的内在机制。下行抑制系统在偏头痛的镇痛中占重要地位，最新研究发现前扣带回皮层突触传递的长时程增强参与偏头痛的慢性化，而ONS是否通过激活下行抑制系统以及改变皮层突触可塑性发挥治疗作用尚存争议。本研究首先建立慢性偏头痛大鼠模型，对比ONS干预前后大鼠疼痛相关行为及痛阈改变，应用组织化学及分子生物学方法观察痛觉传导通路的激活情况及内源性神经肽的释放改变，并且运用电生理方法分析ONS对皮层突触可塑性的影响，从而深入探讨ONS治疗偏头痛的作用机制，为非药物手段精准治疗偏头痛提供理论基础。

偏头痛是临床上最常见的原发性头痛之一，世界卫生组织将其列为全球第二大致残性疾病，在中国人群中偏头痛的发病率高达9.3%。但由于偏头痛治疗药物副作用大，患者接受程度不高，神经调制作为安全有效的非药物治疗手段逐渐受到关注。前期开展的随机对照临床研究已经明确了经皮枕神经电刺激(occipital nerve stimulation,ONS）治疗偏头痛的有效性及安全性，但临床研究中安慰剂效应难以完全除外，且ONS治疗偏头痛的具体作用机制尚不明确。因此，本课题拟设计动物实验分别通过无创及有创枕神经电刺激干预偏头痛大鼠模拟临床治疗，进一步探索ONS治疗偏头痛的内在机制。首先通过炎症汤刺激上矢状窦旁硬脑膜成功建立了慢性偏头痛大鼠模型，在此基础上对其进行反复经皮枕神经电刺激（tONS）及侵入性枕神经刺激（iONS），首先应用行为学评估对比ONS干预前后大鼠疼痛相关行为及痛阈改变，并利用免疫荧光、免疫印迹、透射电镜等技术手段，观察痛觉传导通路的激活情况、内源性神经肽以及突触可塑性相关蛋白的表达改变，并进一步就ONS对前扣带回皮层突触超微结构的影响加以分析。研究结果发现反复炎症汤刺激可明显诱发大鼠痛觉敏感及增加痛觉相关行为，tONS及iONS均可有效改善痛觉相关行为，其中tONS在干预2天后开始起效，而侵入性枕神经刺激在干预后12小时即可起效并可持续至24小时。免疫荧光结果发现无创枕神经电刺激干预可以明显逆转多个痛觉传导通路中c-fos及降钙素基因相关肽的表达上调。在探索神经肽随时间变化趋势时，免疫组化结果提示垂体腺苷酸环化酶激活肽在三叉神经节内出现先释放增多后慢性消耗的趋势。Western-blot研究结果提示蛋白突触后致密物PSD-95在偏头痛模型组明显表达增加，iONS干预组PSD-95表达有所下降但仍明显高于对照组。透射电镜研究结果提示侵入性ONS可逆转反复化学刺激所导致的前扣带回皮层突触超微结构及突触传递的改变。上述结果证明改善三叉神经颈部复合体的激活、改变三叉神经血管系统中感觉神经肽表达以及调节前扣带回皮层突触结构及功能可塑性可能是ONS治疗偏头痛的关键机制。本研究在动物实验中再次证实了无创及有创枕神经电刺激治疗偏头痛的有效性，并从多角度探讨了枕神经电刺激治疗偏头痛可能的作用机制，为非药物手段治疗偏头痛增添了有力证据及理论基础。