Rodent Behavioral Model of Ongoing Headache Pain

描述(申请人提供)：疼痛领域一直需要开发更好的方法来评估动物的疼痛，特别是与触觉或热过敏相反的“自发”或持续疼痛的分析。头痛领域，特别是多年来，一直遭受着没有行为测试的严重限制。目前的证据支持这样一种观点，即偏头痛和其他头痛是由最终进入脑膜的感觉神经激活引起的。因此，实验诱导的这些脑膜神经末梢的激活被用于研究头痛的机制。一项重大突破是证明了化学脑膜(硬脑膜)刺激导致清醒大鼠面部痛觉异常，首次提供了动物头痛的行为模型。我们现在建议在头痛的研究上寻求进一步的突破：对化学刺激硬脑膜后大鼠“自发”行为的变化进行新的观察。核心发现是对正常探索行为的抑制，以及随之而来的“休息”行为或安静清醒的数量增加。这可能被认为是更普遍的抑制先天行为/运动活动的现象的一个例子，这已经被用作评估自发疼痛的一种方法。硬脑膜刺激还引起了一段短暂的同侧面部“梳理”或摩擦，这主要是用后爪而不是前爪完成的。关键的是，这些行为改变可被Triptan预治疗部分阻断。我们现在建议通过在大鼠身上更详细地描述这一模型来追求这些发现，然后使用同样的方法在小鼠身上也建立这一模型。在大鼠身上进行的实验将：1)评估该模型的剂量-反应曲线，以找到足以产生强有力的行为反应的最低应用炎症介质浓度；2)测量长期应用的介质的脑脊液水平以调查通过硬脑膜的扩散量；3)在接受硬膜刺激的大鼠中寻求脑电频谱变化的初步结果，包括与安静清醒的增加相关联的theta活动的增加。在小鼠身上的研究将比较不同菌株的伤害性反应和曲普坦敏感性，并确定高反应菌株和低反应菌株的顺序是否与以前在其他疼痛模型中发现的不同。这将为未来识别硬脑膜刺激反应和Triptan敏感性的基因决定因素开辟一条途径。除了“自发”疼痛与刺激诱发的超敏反应之间存在潜在相关性的意义外，这个模型还有一个优点，那就是它避免了应用von Frey检验的必要性，而von Frey检验尤其困难 在老鼠身上。将进行补充研究，以检查神经激活的解剖学标记(FOS和PERK)，以将背角浅层或深层以及其他中央区域的激活与行为反应的大小相关联。

DESCRIPTION (provided by applicant): The pain field has had an ongoing need to develop better ways of assessing pain in animals, especially assays of "spontaneous" or ongoing pain as opposed to tactile or thermal hypersensitivity. The headache field in particular for many years suffered from the severe limitation of having no behavioral assay. Current evidence now supports the idea that migraine and other headaches result from the activation of the sensory nerves that end in the meninges. Consequently, experimentally induced activation of these meningeal nerve endings has been used to investigate headache mechanisms. A major breakthrough was the demonstration that chemical meningeal (dural) stimulation induced facial allodynia in awake rats, providing for the first time a behavioral model of headache in animals. We now propose to pursue what we believe is a further breakthrough for the study of headache: a new observation of a change in "spontaneous" behavior following chemical stimulation of the dura in rats. The core finding is a suppression of the normal exploratory behavior, and a concomitant increase in the amount of "resting' behavior or quiet wakefulness. This may be considered an example of the more general phenomenon of suppression of an innate behavior/locomotor activity, which has been used as an approach for assessing spontaneous pain. The dural stimulus also induced a brief initial period of ipsilateral facial "grooming" or rubbing that was done primarily with the hindpaw rather than the forepaw. Critically, these behavioral changes were partially blocked by triptan pre-treatment. We now propose to pursue these findings by characterizing this model in more detail in the rat, and by then using the same methods to also establish this model in mice. Experiments in the rat will: 1) evaluate the dose-response curve for this model, in order to find the lowest concentration of applied inflammatory mediators that is sufficient for producing a robust behavioral response, 2) measure CSF levels of the durally applied agents to investigate the amount of diffusion through the dura, and 3) pursue preliminary findings of changes in the EEG spectrum, consisting of an increase in theta activity, correlated with the bouts of increased "resting" of quiet wakefulness, in the rats that received the dural stimulus. Studies in mice will compare different strains for both their nociceptive response and triptan sensitivity, and determine whether the order of high- vs low-responding strains differs from that found previously for other pain models. This will open an avenue for future studies into identifying genetic determinants of the response to dural stimulation and triptan sensitivity. Besides the significance of having a potential correlate of "spontaneous" pain as opposed to stimulus-evoked hypersensitivity, this model also has the advantage that it avoids the necessity for applying von Frey testing, which is especially difficult in the mouse. Complementary studies will be carried out to examine anatomical markers of neural activation (fos and pERK) to correlate activation in superficial or deep dorsal horn laminae, as well as other central regions, with the magnitude of the behavioral response.