瞬时受体电位离子通道A1对慢性偏头痛大鼠模型的作用及氟桂利嗪对其影响

目的本实验通过炎性汤(IS)反复刺激大鼠上矢状窦区硬脑膜疼痛感受器建立慢性偏头痛(CM)大鼠模型,研究瞬时受体电位离子通道A1(TRPA1)及降钙素基因相关肽(CGRP)在CM大鼠模型中的作用,探讨TRPA1在CM发生发展中的可能作用及氟桂利嗪对其影响。方法清洁级SD雄性大鼠48只,体重250~300 g,按随机数字法分为4组(n=12):正常对照组(A组)、假手术组(B组)、CM模型组(C组)及药物干预组(D组)。注射试剂1 h后安静环境中进行大鼠行为学观察及机械刺激缩足反应阈值(PWMT)测定。采用Elisa、Real-Time PCR及Western-Blot技术检测大鼠硬脑膜、三叉神经节(TG)及三叉神经脊束核尾核(TNC)组织部位TRPA1及CGRP表达情况。结果与A组、B组相比较,C组大鼠行为学评分明显升高,PWMT测定值降低,大鼠硬脑膜、TG及TNC组织部位中CGRP及TRPA1表达量均明显上调,差异有统计学意义(P0.05);与C组相比较,D组大鼠行为学评分降低,PWMT测定值升高,硬脑膜、TG及TNC组织部位CGRP及TRPA1表达量均下调,差异有统计学意义(P0.05)。结论 I TRPA1受体可能参与CM发作的病理生理过程;氟桂利嗪可能通过影响TRPA1受体表达,引起CGRP表达下调,从而缓解CM症状。     

侧脑室注射腺苷A1受体激动剂对硝酸甘油偏头痛模型大鼠的影响

目的通过对硝酸甘油偏头痛模型大鼠侧脑室注射腺苷A1受体激动剂(R-phenylisopropyl-adenosine,R-PIA),探讨腺苷在偏头痛中的作用及机制。方法观察各组大鼠不同时间段内挠头、爬笼次数及心率变化,采用Elisa、免疫组织化学法、Western blot技术检测血液、三叉神经节(trigeminal ganglion,TG)、三叉神经脊束核尾核(spinal trigeminal nucleus caudalis,TNC)处降钙素基因相关肽(calcitonin gene-related peptide,CGRP)的表达。结果(1)与模型组相比,治疗组大鼠挠头、爬笼次数均减少并呈剂量依赖性(P0.05),且大鼠心率没有明显变化;(2)治疗组大鼠血液、TG、TNC部位CGRP的表达较模型组均降低(P0.05)。结论激活的腺苷A1受体能够通过抑制神经源性炎症反应及痛觉传导,从而抑制三叉神经血管系统的激活及痛觉敏化,对偏头痛产生镇痛作用。     

偏头痛模型大鼠相关活性物质表达

目的研究磷酸化的细胞外信号调节激酶(the phosphorylated form of the extracellular signal-regulated kinase,p-ERK)、降钙素基因相关肽(calcitonin gene-related peptide,CGRP)及环氧化酶-2(cyclooxygenase-2,COX-2)在偏头痛模型大鼠硬脑膜、三叉神经节和三叉神经脊束尾核组织中的表达及其相关性,为探讨偏头痛发病机制提供依据。方法将60只雄性SD大鼠随机分为空白组、生理盐水组、硝酸甘油组和电刺激组;硝酸甘油组和生理盐水组根据注射后时间再分别分为30 min、1h和3h组;电刺激组再分为电刺激三叉神经节(ESTG)模型组、假手术组和尼美舒利干预组。采用免疫组化染色观察大鼠硬脑膜、三叉神经节和三叉神经脊束尾核p-ERK、CGRP、COX-2的表达。结果 (1)硝酸甘油组大鼠硬脑膜、三叉神经节和三叉神经脊束尾核的pERK、CGRP、COX-2表达均明显高于生理盐水组(均P0.01),ESTG大鼠不同部位组织的p-ERK、CGRP、COX-2表达均明显高于假手术组和空白组(均P0.01);(2)p-ERK表达在注射硝酸甘油后的30min组均高于1h组和3h组,后随时间增加其表达逐渐降低(均P0.01);(3)尼美舒利干预组大鼠不同组织中p-ERK、CGRP、COX-2的表达均低于ESTG模型组(P0.05)。结论 (1)p-ERK、CGRP、COX-2表达上调与偏头痛的炎性反应和疼痛敏化有关,其中p-ERK可能参与偏头痛早期过程;(2)偏头痛过程中,p-ERK、CGRP和COX-2蛋白之间有密切联系。     

天麻制剂通过腺苷途径治疗偏头痛相关的分子机制研究

目的探讨天麻制剂各有效成分对偏头痛模型大鼠的降钙素基因相关肽(calcitonin gene-related peptide,CGRP)与腺苷A1受体(adenosine A1 receptor,A1R)表达的影响。方法将SPF级雄性SD大鼠84只随机分为7组(n=12):假手术组(A组/阴性对照组)、电刺激三叉神经节(electrical stimulation of the trigeminal ganglion,ESTG)模型组(B组)、舒马普坦干预组(C组/阳性对照组)、天麻素干预组(D组)、对羟基苯甲醇干预组(E组)、香英兰醇干预组(F组)、β-谷甾醇干预组(G组)。通过建立ESTG模型,采用酶联免疫吸附测定(enzyme-linked immuno sorbent assay,Elisa)、免疫荧光及Western-Blot技术检测天麻制剂各有效成分对CGRP与A1R表达的影响。结果与A组相比,B组大鼠三叉神经节(trigeminal ganglia,TG)、三叉神经脊束尾核(trigeminal nucleus caudalis,TNC)中的CGRP表达明显增高,A1R的表达明显降低,差异具有统计学意义(P 0. 01)。与B组相比,C、D组大鼠TG、TNC中的CGRP表达明显降低,A1R的表达明显增高,差异具有统计学意义(P 0. 01);而E、F、G组与B组之间差异无统计学意义(P0. 05)。与C组相比,D组大鼠TG、TNC中的CGRP、A1R的表达无明显差异(P 0. 05)。结论预防应用天麻素,与舒马普坦一样可对偏头痛发作起到一定保护作用,而香英兰醇、对羟基苯甲醇及β-谷甾醇对缓解偏头痛的作用疗效甚微,且天麻制剂有效成分中天麻素可通过激活A1R及抑制CGRP表达来抑制偏头痛的发生。     

低剂量左旋多巴对帕金森病大鼠纹状体乙酰胆碱M1和M2受体表达的影响

目的探讨低剂量的左旋多巴对帕金森病(PD)大鼠纹状体乙酰胆碱M1、M2受体表达的影响。方法将成功建模的20只PD大鼠随机分为模型对照组、左旋多巴干预7d、14d、21d组(每组5只),另将5只正常大鼠设为空白对照组。采用免疫组化技术测定纹状体乙酰胆碱M1和M2受体的表达情况。结果 M1受体蛋白在帕金森病大鼠中的表达高于空白对照组,药物干预7d、14d后M1受体蛋白表达较模型对照组明显降低(P0.05),但在药物干预21d后M1受体蛋白表达明显回升(P0.05);M2受体蛋白表达在帕金森病大鼠模型对照组较空白对照组明显下降(P0.05),但在用药物进行干预后较空白对照组无明显回升(P0.05)。结论帕金森病大鼠在低剂量的左旋多巴干预后M1受体蛋白的表达是一个动态变化变化过程,而M2受体蛋白的表达在药物干预后较空白对照组无明显变化。     

电刺激三叉神经节诱导偏头痛大鼠脑膜非特异炎症

目的 电刺激三叉神经节建立偏头痛大鼠模型,观察偏头痛大鼠硬脑膜的非特异炎症及5-HTIB/1D受体、降钙素基因相关肽物质(CGRP)在硬脑膜上的分布.方法 采用体重250～300克的雄性SD大鼠,单侧电刺激大鼠三叉神经节建立偏头痛大鼠模型,取大鼠硬脑膜,(1)行HE染色观察非特异炎症;(2)行免疫荧光法检测硬脑膜上5-HT1B/1D受体和CGRP的表达.结果 偏头痛大鼠模型成功建立得到两方面证实:(1)刺激侧大鼠咀嚼肌收缩,口鼻分泌物增多;(2)硬脑膜HE染色显示刺激侧出现炎症反应.初步完成5-HT1B/1D受体及CGRP在硬脑膜上的定位.结论 电刺激三叉神经节可诱导偏头痛大鼠脑膜非特异炎症,5-HT1B/1D受体和CGRP可能在偏头痛疼痛的产生和维持中起着重要的作用.     

舒马普坦通过细胞外信号调节激酶1/2和c-Jun氨基末端激酶信号通路下调三叉神经节内降钙素基因相关肽的表达

目的 探讨舒马普坦对大鼠三叉神经节(TG)离体培养后降钙素基因相关肽(CGRP)表达水平的影响.方法 采用TG离体培养模型,按数字随机表法将54个TG随机分为新鲜组(6个)、对照组(6个)和实验组(7个亚组,每亚组6个,共42个).实验组TG培养液中分别加入4种不同浓度舒马普坦,细胞外信号调节激酶1/2 (ERK1/2)信号通路阻滞剂U0126和PD98059,c-Jun氨基末端激酶(JNK)信号通路阻滞剂SP600125,孵育24h后免疫组织化学染色检测CGRP免疫反应(CGRP-ir)阳性细胞表达,实时定量PCR检测CGRP-mRNA表达量,Western blot定量磷酸化ERK1/2( pERK1/2)和JNK (pJNK)蛋白水平.结果 离体培养24h后,TG内CGRP-ir(+)细胞表达明显增高,0.1和0.5 mg/ml舒马普坦组CGRP-ir(+)细胞百分比、阳性面积、累积吸光度、平均吸光度、CGRP-mRNA水平较对照组明显下降(tPCP=8.652、26.382,tares=6.220、13.917,tIA=5.606、15.904,tM14=2.661、21.748,tmRNA=8.032、15.675,均P＜0.05);而0.02和2.50 mg/ml舒马普坦与对照组CGRP表达差异无统计学意义.Western blot结果显示:0.50 mg/ml浓度舒马普坦显著降低TG内pERKl/2、pJNK水平,降低程度分别接近于10μmol/L的U0126、PD98059和SP600125.结论 一定浓度舒马普坦通过细胞内ERKl/2、JNK信号通路下调大鼠TG离体培养后CGRP的过度表达.     

伏核内注射TRPV1拮抗剂对大鼠体质量及脂肪积累中枢调节的影响

目的 研究TRPV1拮抗剂辣椒卓平(CPZ)作用于伏核对大鼠体质量及脂肪积累的影响,探讨其对神经病理性肥胖的治疗作用. 方法 40只SD大鼠采用随机数字表法分为5组,每组8只,分别为:对照组,不作任何处理;A组,伏核注射CPZ 1 nmol/mL;B组,伏核注射CPZ 10nmol/mL;C组,偏离伏核靶点注射CPZ 10 nmol/mL;D组,背侧纹状体内注射CPZ 10 nmol/mL;后4组注射剂量为1 μL,每侧每天1次,连续给药3d.观察注射后1周及3周大鼠体质量相对于对照组的变化及各组大鼠体质量增长速度的变化;解剖各组大鼠观察其体脂含量. 结果 A组大鼠在给药1周后体质量为起始体质量的(126.31±10.25)％,B组大鼠给药1周后体质量为起始体质量的(115.87±13.90)％,2组大鼠均较对照组大鼠(148.78±6.98)％的增幅明显降低,差异均有统计学意义(P＜0.05).给药3周后B组大鼠体质量为起始体质量的(132.82±15.8)％,仍较对照组大鼠(164.86±6.34)％的增幅明显降低,差异有统计学意义(P＜0.05).给药1周后A、B组大鼠平均每日体质量增长(3.2±0.78)g和(3.2±0.53)g,较对照组(10.26±1.76)g明显降低,差异有统计学意义(P＜0.05).给药3周后B组大鼠平均每日体质量增长(5.46±0.94)g,仍然低于对照组(10.33±1.37)g,差异有统计学意义(P＜0.05).解剖结果显示B组大鼠体脂含量明显低于对照组,差异有统计学意义(P＜0.05). 结论 CPZ拮抗伏核TRPV1受体对大鼠体质量增长及脂肪积累有较明显的抑制性中枢调节作用.TRPV1拮抗剂有可能成为理想的特异性神经病理性肥胖的治疗药物.     

TNF-α在偏头痛大鼠模型三叉神经节内的表达

目的探讨硝酸甘油(NTG)致偏头痛大鼠模型三叉神经节(TG)内肿瘤坏死因子-α(TNF-α)的表达情况。方法雄性SD大鼠随机分为空白对照组、生理盐水对照组和偏头痛模型组,每组8只。偏头痛模型组大鼠予颈背部皮下注射NTG,生理盐水对照组大鼠予注射0.9%生理盐水,空白对照组不做任何处理。观察各组大鼠疼痛行为学并进行评分比较,采用免疫荧光染色法检测各组大鼠TG内TNF-α表达情况。结果偏头痛模型组大鼠的疼痛行为学评分较两对照组明显增高(P 0.01),且TG内TNF-α表达水平也显著高于两对照组(P 0.01),而两对照组间均无明显差异(P0.05)。结论 TNF-α在偏头痛大鼠模型TG内表达显著增多,这在偏头痛的发病机制中可能具有一定的意义。     

青藤碱对偏头痛模型大鼠血浆CGRP、SP含量及脑干5-HT表达的影响

目的 观察青藤碱对偏头痛模型大鼠血浆降钙素基因相关肽(CGRP)、P物质(SP)含量及脑干5-羟色胺(5-HT)表达的影响,探讨青藤碱治疗偏头痛的作用机制,为开发治疗偏头痛新药提供实验依据.方法 60只Wistar大鼠(雌雄各半)随机分为:空白对照组、模型组、舒马普坦组、青藤碱低、中、高剂量治疗组,建立硝酸甘油的动物模型.以舒马普坦为阳性对照组,用放免法测定大鼠血浆CGRP、SP含量;免疫组化SBAC法检测脑干5-HT阳性表达.同时观察大鼠的行为学变化.结果 (1)各组大鼠血浆CGRP、SP含量差异无统计学意义(P＞0.05);(2)青藤碱各组和舒马普坦组脑干5-HT表达明显增多,与模型组和空白组相比较差异有统计学意义P＜0.01),而青藤碱中剂量组脑干5-HT表达和舒马普坦组相比较差异无统计学意义P＞0.05).(3)大鼠行为学观察显示,药物干预组对偏头痛模型大鼠行为症状随时间延长而逐渐消失.结论 (1)青藤碱对偏头痛模型大鼠具有镇痛作用,其机制可能是通过偏头痛发作时调节脑干5-HT能系统的活性,起到镇痛作用.(2)青藤碱对偏头痛模型大鼠行为症状学有改善作用.     

PACAP-38 but not VIP induces release of CGRP from trigeminal nucleus caudalis via a receptor distinct from the PAC1 receptor

Objective

To investigate if PACAP and VIP have an effect on CGRP release or NOS activity in the trigeminal ganglion and trigeminal nucleus caudalis and if there can be a difference in effect between PACAP and VIP on these two systems. Furthermore, we investigate if PACAP co-localize with CGRP and/or nNOS in the two tissues.

Background

The structurally related neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide-38 (PACAP-38) partially share receptors and are both potent vasodilators. However, PACAP-38 but not VIP is an efficient inducer of migraine attacks in migraineurs. Calcitonin gene-related peptide (CGRP) and nitric oxide (NO) are two signaling molecules known to be involved in migraine.

Methods

Rat tissue was used for all experiments. Release of CGRP induced by VIP and PACAP in dura mater, trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC) was quantified by EIA. Regulation of NOS-enzymes caused by VIP and PACAP was investigated in dura mater, TG and TNC by measuring the conversion of l-[³H]arginine to l-[³H]citrulline. Co-expression of PACAP, neuronal nitric oxide synthase (nNOS) and CGRP was explored by immunohistochemistry in TG and TNC. mRNA expression studies of VPAC₁, VPAC₂ and PAC₁-receptors were performed by qRT-PCR.

Results

PACAP-38 administered in increasing concentrations caused a concentration-dependent CGRP-release in the TNC, but not in TG. VIP was without effect in both tissues examined. The PAC₁ receptor agonist maxadilan had no effect on CGRP release and the PAC₁ antagonist M65 did not inhibit PACAP-38 induced CGRP release. PACAP-38 or VIP did not affect NOS activity in homogenates of TG and TNC. Quantitative PCR demonstrated the presence of VPAC₁, VPAC₂ and PAC₁ receptors in TG and TNC. Immunohistochemistry of PACAP and CGRP showed co-expression in TG and TNC. PACAP and nNOS were co-localized in TG, but not in TNC. PACAP was found to co-localize with glutamine synthetase in TG satellite glial cells.

Conclusion

PACAP-38 cause release of CGRP from TNC but not from TG. We suggest that the release is not caused via activation of PAC₁, VPAC₁ or VPAC₂ receptors. PACAP has no effect on NOS activity in TG or TNC. In TG PACAP was found in neuronal cells and in satellite glial cells. It co-localized with CGRP and nNOS in the neuronal cells. In TNC PACAP was co-localized with CGRP but not with nNOS.     

Expression of ASIC3 in the Trigeminal Nucleus Caudalis Plays a Role in a Rat Model of Recurrent Migraine

Acid-sensing ion channel 3 (ASIC3) is abundant in the trigeminal nervous system and is most sensitive to a slight pH decrease. Recent studies have indicated that ASIC3 in the peripheral trigeminal ganglia is likely involved in the pathogenesis of migraine pain. However, it is unclear whether this receptor plays a role in recurrent migraine, namely, migraine chronicity. Here, we aimed to investigate the role of ASIC3 in an animal model of recurrent migraine (RM). In this study, we established a rat model of RM through repeated administration of inflammatory soup (IS) onto the dura. Then, we tested the mechanical pain thresholds of the face and hindpaws by von Frey filaments. qRT-PCR, Western blot and immunofluorescence labelling were used to detect the expression and localization of ASIC3 in the trigeminal nucleus caudalis (TNC). The protein levels of calcitonin gene-related peptide (CGRP), its receptor component receptor activity modifying protein 1 (RAMP1) and c-Fos were analysed following treatment with the ASIC3 inhibitor APETx2 and activator 2-guanidine-4-methylquinazoline (GMQ). We found decreased pain thresholds after repeated dural inflammatory stimulation, which suggested the establishment of an RM model. Based on this model, we observed elevated expression of ASIC3 in the TNC group compared to that in the Sham group. ASIC3 was primarily expressed in neurons but not in astrocytes of the TNC. Moreover, APETx2 attenuated tactile allodynia and significantly decreased the expression of c-Fos, CGRP and RAMP1, while GMQ aggravated these effects compared to those observed in the IS + vehicle group. These findings indicate a critical role of ASIC3 channels in the pathophysiology of RM, and ASIC3 might represent a potential therapeutic target to prevent the progression of migraine.     

Effects of eletriptan on the peptidergic innervation of the cerebral dura mater and trigeminal ganglion, and on the expression of c-fos and c-jun in the trigeminal complex of the rat in an experimental migraine model

Nociceptive axons and terminals in the supratentorial cerebral dura mater display an intense calcitonin gene-related peptide (CGRP) immunoreactivity. In an experimental migraine model, it has been shown that electrical stimulation of the rat trigeminal ganglion induced an increase in the lengths of CGRP-immunoreactive axons, increased size and number of pleomorphic axonal varicosities in the dura mater, and an increased number of c-jun and c-fos protein-expressing nerve cells in the trigeminal complex. We demonstrate the effect of the highly specific and moderately lipophilic serotonin agonist eletriptan (Pfizer) which prevents the effects of electrical stimulation in the dura mater. Eletriptan also affected the caudal trigeminal complex; it markedly reduced the numbers of the oncoprotein-expressing cells, mainly after stimulation and to some extent also in nonstimulated animals. Eletriptan also affected expression of CGRP in perikarya of trigeminal ganglion cells, insofar as the number of small nerve cells exhibiting a compact CGRP immunoreaction was decreased to one quarter of the original value. In all these respects, eletriptan acted in a similar way to sumatriptan, with the notable exception that eletriptan also blocked the stimulation-induced effects in the nucleus caudalis trigemini and the upper cervical spinal cord (trigeminal complex), whereas sumatriptan did not. It is concluded that eletriptan, acting on perikarya and both the peripheral and the central axon terminals of primary sensory neurons, exerts its antimigraine effect by an agonist action on 5-HT1B/1D receptors throughout the entire trigeminal system, probably by passing the blood-brain-barrier because of its lipophilic character.     

偏头痛大鼠硬脑膜肥大细胞脱颗粒与神经源性炎症相关因子的变化

目的 观察偏头痛大鼠硬脑膜肥大细胞脱颗粒与神经源性炎症相关因子的变化,探讨偏头痛疼痛产生的可能机制.方法 64只SD大鼠随机分为刺激组(32只)和假手术组(32只).电刺激大鼠单侧三叉神经节建立偏头痛模型,放射免疫法测定刺激侧颈静脉血中降钙素基因相关肽(CGRP)的含量.酶联免疫吸附法测定刺激侧颈静脉血中组胺和硬脑膜中前列腺素E2(PGE2)的含量,甲苯胺蓝染色观察硬脑膜肥大细胞的数量及脱颗粒百分率,免疫组织化学染色法、免疫蛋白质印迹技术观察硬脑膜中环氧化酶-2(COX-2)的阳性细胞数及蛋白表达.结果 假手术组和刺激组颈静脉血中CGRP含量分别为(59.20±11.66)pg/ml和(82.84±16.24)pg/ml(t=-3.34);组胺含量分别为(9.87±0.88)ng/ml和(11.59±1.20)ng/ml(t=-3.27);硬脑膜中肥大细胞数量分别为15.46±2.40和11.63±1.67(t=3.71),脱颗粒百分率分别为14.09%±4.53%、29.10%±9.39%(t=-4.07).两组硬脑膜中PGE2的含量分别为(80.70±10.60)pg/ml和(382.30±20.90)pg/ml(t=-16.674);硬脑膜中COX-2阳性细胞数分别为42.00±18.40和139.00±20.50(t=-7.994),COX-2蛋白表达(吸光度值)分别为19.50±9.20和359.20±21.90(t=-5.190).两组间比较,上述指标差异均有统计学意义(P＜0.05).结论 电刺激单侧三叉神经节可诱导硬脑膜肥大细胞脱颗粒及神经源性炎症的产生,相关炎症因子的改变可能是偏头痛疼痛发生的重要病理生理基础.     

Colocalization of CGRP with 5-HT1B/1D receptors and substance P in trigeminal ganglion neurons in rats

Vasodilatation in the dura mater has been implicated in migraine pathogenesis. Anti-migraine triptan drugs block vasodilatation by binding to 5-HT1B/1D receptors localized on the peripheral sensory terminals and dural blood vessel smooth muscles. Previous studies suggest that calcitonin gene-related peptide (CGRP) released from Adelta-fibres plays a more important role than substance P (SP) released from C-fibres in inducing dural vasodilatation and that one of the antimigraine mechanisms of triptan drugs is inhibiting CGRP release. In the present study, the relationship between CGRP and 5-HT1B/1D receptors, and between CGRP and SP in the trigeminal ganglion neurons in rats was examined by double immunohistochemical staining. CGRP, 5-HT1B, 5-HT1D and SP-positive trigeminal ganglion neurons were all predominantly small and medium-sized. In the trigeminal ganglia, approximately 50% of CGRP-positive neurons were 5-HT1B positive. Similarly, approximately 55% of CGRP-positive neurons were 5-HT1D immunoreactive. Approximately 50% of CGRP-positive neurons were SP-positive, while 93% of SP-positive neurons were CGRP-positive, suggesting that nearly all SP-positive neurons also contain CGRP. The fibre types of the 5-HT1B- and 5-HT1D-positive neurons were further investigated with an antibody against the A-fibre marker 200-kDa neurofilaments (NF200). Approximately 46% of the 5-HT1B-positive and 43% of the 5-HT1D-positive trigeminal ganglion neurons were also NF200 positive, indicating that many A-fibre trigeminal neurons express 5-HT1B or 5-HT1D receptors. These results support the hypothesis that one important action of antimigraine drugs is the inhibition of CGRP release and that Adelta-fibres may play an important role in migraine pathogenesis.     

Vasoactive Intestinal peptide modulates c‐Fos activity in the trigeminal nucleus and dura mater mast cells in sympathectomized rats

Neurogenic inflammation in the dura mater caused by trigeminal nociceptive activation has been implicated in the pathophysiology of migraine. Vasoactive intestinal polypeptide (VIP) is a powerful neuroprotective neuropeptide that can modulate mast cell behavior. Migraine is also associated with sympathetic insufficiency. This study investigates the effects of VIP on the number of mast cells in the dura mater and on c‐Fos expression in the trigeminal nucleus of sympathectomized rats. Experiments were carried out with 32 Sprague‐Dawley male rats with body weights of 200–250 g. In the sympathectomized group, the left superior cervical sympathetic ganglion was removed. In the sympathectomized + VIP group, postoperative VIP 25 ng/kg/day (0.2 ml) was administered for 5 days. In the sham group, the ganglion and nerves were exposed but not dissected. Dura maters were stained with toluidine blue, and brainstems were labeled by indirect immunohistochemistry for c‐Fos. Sympathectomy significantly increased the number of mast cells in both the ipsilateral and the contralateral dura mater (P < 0.001). VIP decreased the number of mast cells in both sides of the dura mater in sympathectomized rats. VIP also decreased c‐Fos expression in the ipsilateral trigeminal nucleus of sympathectomized rats (P < 0.001). In the context of an experimental superior cervical ganglionectomy model of migraine, VIP is an efficient modulator of neurogenic inflammation of the dura. © 2014 Wiley Periodicals, Inc.     

Calcitonin receptor-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and calcitonin gene-related peptide (CGRP) immunoreactivity in the rat trigeminovascular system: differences between peripheral and central CGRP receptor distribution

Calcitonin gene-related peptide (CGRP) is a key mediator in primary headaches including migraine. Animal models of meningeal nociception demonstrate both peripheral and central CGRP effects; however, the target structures remain unclear. To study the distribution of CGRP receptors in the rat trigeminovascular system we used antibodies recognizing two components of the CGRP receptor, the calcitonin receptor-like receptor (CLR) and the receptor activity-modifying protein 1 (RAMP1). In the cranial dura mater, CLR and RAMP1 immunoreactivity (-ir) was found within arterial blood vessels, mononuclear cells, and Schwann cells, but not sensory axons. In the trigeminal ganglion, besides Schwann and satellite cells, CLR- and RAMP1-ir was found in subpopulations of CGRP-ir neurons where colocalization of CGRP- and RAMP1-ir was very rare ( approximately 0.6%). CLR- and RAMP1-ir was present on central, but not peripheral, axons. In the spinal trigeminal nucleus, CLR- and RAMP1-ir was localized to "glomerular structures," partly colocalized with CGRP-ir. However, CLR- and RAMP1-ir was lacking in central glia and neuronal cell bodies. We conclude that CGRP receptors are associated with structural targets of known CGRP effects (vasodilation, mast cell degranulation) and targets of unknown function (Schwann cells). In the spinal trigeminal nucleus, CGRP receptors are probably located on neuronal processes, including primary afferent endings, suggesting involvement in presynaptic regulation of nociceptive transmission. Thus, in the trigeminovascular system CGRP receptor localization suggests multiple targets for CGRP in the pathogenesis of primary headaches.     

Activation of 5-HT(1B/1D) receptor in the periaqueductal gray inhibits nociception

It is considered that the site of action of the abortive antimigraine compounds acting at serotonin, 5-HT(1B/1D,) receptors (triptans) is the trigeminovascular system. We tested whether there is a non-trigeminal site of action. The 5-HT(1B/1D) agonist, naratriptan, was microinjected into the ventrolateral periaqueductal gray (vlPAG), and activity in the trigeminal nucleus caudalis (TNC) was monitored. Recordings were made from 20 nociceptive neurons in the dorsal horn of the TNC that received convergent input from the dura mater and face. Responses of neurons to dural, facial cutaneous and corneal stimulation were studied before and after injection of naratriptan. Naratriptan decreased the excitability to electrical stimulation of the dura mater as the A-fiber response decreased by 24 +/- 4.1% (p < 0.001) and the C-fiber response decreased by 42 +/- 8.2% (p < 0.001). Spontaneous activity was decreased by 38 +/- 7.5% (p < 0.001). After injection, the mechanical thresholds of the dura mater increased from (n = 14, p < 0.01). Responses to stimulation of the face and cornea were not altered by injection of naratriptan. These results suggest that 5-HT(1B/1D) receptor activation in the vlPAG activates descending pain-modulating pathways that inhibit dural, but not facial and corneal nociceptive input. These findings have implications for the understanding of the action of triptans in migraine and cluster headache, suggesting that brain loci other than the trigeminal nucleus may play a role in the clinical action of triptans.