PACAP-PAC1受体通路参与偏头痛发病的机制研究

Previous studies have demonstrated that pituitary adenylate cyclase-activating polypeptide(PACAP) played an important role in lots of migraine-related mechanisms, such as vasodilation, activation of trigeminovascular system, nitric oxide pathway, central sensitization and neurogenic inflammation. However, the molecular mechanism of PACAP in migraine is still unclear. The aim of this study is to explore whether PACAP combined with its special receptor PAC1 will cause migraine,and its molecular mechanism in the pathogenesis of migraine. We will also study the relationship between PACAP and Calcitonin Gene-Related Peptide(CGRP), the most important migraine-related neurotransmitter in the pathogenesis of migraine. A vascular headache animal model has been set up by our group by electrical stimulating the dura mater surrounding the superior sagittal sinus in conscious adult rats. The change of headache behavior and meningeal blood flow which caused by PACAP in rats is recorded. The observations also include changes caused by PAC1 receptor agonist and antagonist.Then by means of radioimmunoassay, immunohistochemical, microdialysis, Western-blot and RT-PCR, the role of PACAP-PAC1 receptor pathway in the mechanism of migraine is discussed through the aspects of ethology, microcirculation, neurotransmitter, and expression proteomics. Then the following clinical research will be performed to idetify the plasm level of PACAP and CGRP in different course of migraine. The basic theory is provided for screening new medicine in clinical treatment of migraine.

垂体腺苷酸环化酶激活肽(PACAP)在颅内外血管扩张、三叉神经血管反射激活等偏头痛相关机制中发挥作用，而垂体腺苷酸环化酶激活肽Ⅰ型受体(PAC1)为其特异性受体，PACAP-PAC1通路在偏头痛发病中的具体机制，以及与偏头痛发作最重要的递质-降钙素基因相关肽(CGRP)之间的关系仍未完全明确。本研究的基础部分在前期建立的反复电刺激上矢状窦旁硬脑膜偏头痛大鼠模型的基础上，利用放射免疫、免疫荧光、微透析、神经元放电胞外记录、免疫印迹、RT-PCR方法，从行为学、微循环、神经递质、电生理、蛋白共存及表达等方法，探讨PACAP-PAC1通路是否在三叉神经节、三叉神经脊束核尾核、导水管周围灰质通过CGRP的共表达和释放参与偏头痛的发病；临床研究将进一步明确偏头痛患者头痛发作期与发作间期的血浆PACAP、CGRP水平。本研究将为偏头痛的机制研究开辟新方向，也将为探讨和筛选新型抗偏头痛药物提供理论基础。

偏头痛是全球第七大致残性疾病，全球发病率约为11.7%。目前认为CGRP及PACAP均参与三叉神经血管系统激活等重要偏头痛发病机制，但是PACA在偏头痛发病中的具体机制以及与偏头痛发作最重要的递质-降钙素基因相关肽(CGRP)之间的关系仍未完全明确。本项目基础研究部分通过电刺激和化学刺激上矢状窦硬脑膜成功建立了两种偏头痛大鼠模型，利用放射免疫、免疫荧光、免疫印迹等方法，从行为学、神经递质、蛋白共存及表达等方面，探讨PACAP及PACAP相关受体在大鼠三叉神经节（TG）及三叉神经脊束核尾核 (TNC)的表达改变以及与CGRP的共表达情况，结果发现反复电刺激及炎性汤刺激均会造成大鼠面部机械痛阈下降，化学刺激偏头痛大鼠模型TG 和TNC中PACAP表达随着刺激天数的增加呈渐低表达趋势，在此反复刺激过程中PAC1受体在三叉神经节中存在表达上调，VPAC1和VPAC2受体无明显改变；免疫荧光结果发现在TG 和TNC 内PACAP与神经元、PACAP与PAC1受体、PACAP与CGRP在TG有共表达，且共表达量随刺激天数延长而增加。上述研究结果证明这两种大鼠偏头痛模型可以较好地模拟临床上偏头痛慢性化的过程，发现在偏头痛慢性化过程中PACAP呈现先释放增加后逐渐耗竭的规律，而同时PAC1受体表达出现上调，说明PACAP-PAC1受体通路在偏头痛发病机制中起到了至关重要的作用，因此PAC1受体很可能成为未来偏头痛治疗新的靶点。临床研究部分进一步明确偏头痛患者头痛发作间期的血浆PACAP水平，结果发现慢性偏头痛组发作间期血浆PACAP水平明显低于正常对照组和紧张型头痛组；并且通过功能核磁共振的方法发现药物过量性头痛患者与健康对照相比，脑桥、前扣带回、双侧小脑、枕叶、眶额叶皮质、海马旁回以及豆状核等区域的局部一致性下降，证明了药物过量性头痛患者发作期存在脑功能异常。本研究为偏头痛的机制研究开辟新方向，也将为探讨和筛选新型抗偏头痛药物提供理论基础。

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