Vernon Howard, Sun Kaiqi, Zhang Yunfeng, Yu Xian-Min, Sessle Barry J
Canadian Memorial Chiropractic College, Toronto, Ontario, Canada.
J Manipulative Physiol Ther. 2009 Sep;32(7):506-14. doi: 10.1016/j.jmpt.2009.08.012.
This study investigated if central sensitization is induced in the trigeminal subnucleus caudalis (also termed the medullary dorsal horn) and C1 and C2 dorsal horns by noxious stimulation of deep upper cervical paraspinal tissues in a preparation relatively free of surgical trauma.
Adult male Sprague-Dawley rats (275-450 g) were anesthetized intraperitoneally. Animals were then placed in a stereotaxic frame; a small cutaneous incision was made 3 to 4 mm near the bregma in the midline, and an opening into the skull was prepared by a 1/32-inch drill, 1 mm to the left from the midline. An epoxylite-coated tungsten microelectrode was introduced at an 18 degrees angle to enter this small opening on the skull and was then carefully advanced about 16 mm through cortex, cerebellum, and brainstem to reach subsequently histologically confirmed sites in the Vc and upper cervical (C1 and C2) dorsal horn region. Thirty-three, 27, and 15 neurons recorded in medullary, C1, and C2 dorsal horns, respectively, of chloralose/urethane-anesthetized rats were activated by noxious stimulation of mechanoreceptive fields involving V1, V2, and/or V3 trigeminal nerve territories. The inflammatory irritant mustard oil was injected into the deep paraspinal tissues at the level of the left C1-C2 joint. Pre and postinjection receptive field (RF) sizes were mapped by nonnoxious mechanical stimuli and noxious mechanical and heat stimuli.
A 30- to 50-minute increase (mean, 165% +/- 38.1%) in RF size postinjection for 62% of neurons tested was demonstrated, suggesting central sensitization; for most (>70%) neurons, the RF expanded caudally into cervically innervated tissues.
These findings provide the first documentation that deep cervical nociceptive inputs can induce central sensitization in medullary and C1/C2 dorsal horns and suggest that these effects may reflect mechanisms contributing to deep cervical pain and its referral.
本研究探讨在一个相对无手术创伤的实验准备中，对上颈深部椎旁组织进行伤害性刺激是否会在三叉神经尾侧亚核（也称为延髓背角）以及C1和C2背角诱导中枢敏化。
成年雄性Sprague-Dawley大鼠（275 - 450 g）腹腔注射麻醉。然后将动物置于立体定位框架中；在中线靠近前囟处做一个3至4毫米的小皮肤切口，用1/32英寸的钻头在中线左侧1毫米处钻开颅骨。将涂有环氧树脂的钨微电极以18度角插入颅骨上的这个小开口，然后小心地推进约16毫米，穿过皮质、小脑和脑干，随后到达经组织学证实的延髓尾侧亚核（Vc）和上颈（C1和C2）背角区域的位点。分别在水合氯醛/乌拉坦麻醉大鼠的延髓、C1和C2背角记录到的33个、27个和15个神经元，通过对涉及三叉神经V1、V2和/或V3区域的机械感受野进行伤害性刺激而被激活。将炎性刺激物芥子油注射到左侧C1 - C2关节水平的深部椎旁组织中。注射前后的感受野（RF）大小通过非伤害性机械刺激以及伤害性机械和热刺激进行测绘。
62%受试神经元在注射后RF大小增加了30至50分钟（平均，165%±38.1%），提示中枢敏化；对于大多数（>70%）神经元，RF向尾侧扩展至颈部支配组织。
这些发现首次证明了颈部深部伤害性输入可在延髓和C1/C2背角诱导中枢敏化，并表明这些效应可能反映了导致颈部深部疼痛及其牵涉痛的机制。
