Valdman Institute of Pharmacology, St. Petersburg Pavlov State Medical University, Lev Tolstoy street 6/8, St. Petersburg, 197022, Russia.
J Headache Pain. 2012 Jan;13(1):75-82. doi: 10.1007/s10194-011-0404-7. Epub 2011 Nov 25.
Primary headaches are often associated with pain in the maxillofacial region commonly classified under the term "orofacial pain" (OFP). In turn, long-lasting OFP can trigger and perpetuate headache as an independent entity, which is able to persist after the resolution of the main disorder. A close association between OFP and headache complicates their cause and effect definition and leads to misdiagnosis. The precise mechanisms underlying this phenomenon are poorly understood, partly because of the deficiency of research-related findings. We combined the animal models of OFP and headache-the orofacial formalin test and the model of trigeminovascular nociception-to investigate the neurophysiological mechanisms underlying their comorbidity. In anesthetized rats, the ongoing activity of single convergent neurons in the spinal trigeminal nucleus was recorded in parallel to their responses to the electrical stimulation of the dura mater before and after the injection of formalin into their cutaneous receptive fields. Subcutaneous formalin resulted not only in the biphasic increase in the ongoing activity, but also in an enhancement of neuronal responses to dural electrical stimulation, which had similar time profile. These results demonstrated that under tonic pain in the orofacial region a nociceptive signaling from the dura mater to convergent trigeminal neurons is significantly enhanced apparently because of the development of central sensitization; this may contribute to the comorbidity of OFP and headache.
原发性头痛常伴有颌面区域疼痛，通常归类于“口腔面痛”（OFP）一词。反过来，长期的 OFP 可引发和持续头痛作为一个独立的实体，它能够在主要疾病得到解决后持续存在。OFP 和头痛之间的密切关联使得它们的因果关系难以定义，并导致误诊。这种现象的确切机制尚未得到很好的理解，部分原因是相关研究结果的缺乏。我们结合了 OFP 和头痛的动物模型——口腔福尔马林试验和三叉神经血管伤害性感受模型，以研究它们共病的神经生理机制。在麻醉大鼠中，我们在其皮肤感受野中注射福尔马林前后，同时记录了脊髓三叉神经核中单根会聚神经元的持续活动及其对硬脑膜电刺激的反应。皮下福尔马林不仅导致持续活动的双相增加，而且还增强了神经元对硬脑膜电刺激的反应，其时间过程相似。这些结果表明，在口腔区域的紧张性疼痛下，来自硬脑膜的伤害性信号向会聚三叉神经神经元的传递明显增强，显然是因为中枢敏化的发展；这可能有助于 OFP 和头痛的共病。
