Sugimoto T, Fujiyoshi Y, Xiao C, He Y F, Ichikawa H
Department of Oral Anatomy II, Okayama University Dental School, Japan.
J Comp Neurol. 1997 Feb 17;378(3):425-42. doi: 10.1002/(sici)1096-9861(19970217)378:3<425::aid-cne9>3.0.co;2-5.
Substance P (SP) is implicated in transmission of primary afferent nociceptive signals. In primary neurons, SP is colocalized with calcitonin gene-related peptide (CGRP), which is another neuropeptide marker for small to medium primary neurons. CGRP coreleased with SP augments the postsynaptic effect of SP and thereby modulates the nociceptive transmission. This study demonstrates the distribution of CGRP-like immunoreactivity (-ir) and SP-ir in the lower brainstem of normal rats and after trigeminal rhizotomy or tractotomy at the level of subnucleus interpolaris (Vi). By comparing the results obtained from normal and deafferented rats, we analyzed the central projection of trigeminal primary nociceptors. The CGRP-immunoreactive (-ir) trigeminal primaries projected to the entire rostrocaudal extent of the spinal trigeminal nucleus, the principal nucleus (PrV), the paratrigeminal nucleus (paraV), and the lateral subnucleus of solitary tract nucleus (STN) on the ipsilateral side. The trigeminal primaries projecting to the spinal trigeminal nucleus, paraV and STN also contained SP-ir. The ipsilateral trigeminal primaries were the exclusive source of CGRP-ir terminals in the PrV, the Vi and the dorsomedial nucleus within the subnucleus oralis (Vo). The medullary dorsal horn (MDH) and the lateral edge of Vo received convergent CGRP-ir projection from the ipsilateral trigeminal primaries and other neurons. The glossopharyngeal and vagal primaries are candidates for the source of CGRP-ir projection to the Vo and the MDH, while the dorsal root axons supply the MDH with CGRP-ir terminals. In addition, contralateral primary neurons crossing the midline appear to contain CGRP and to terminate in the MDH.
P物质（SP）与初级传入伤害性信号的传递有关。在初级神经元中，SP与降钙素基因相关肽（CGRP）共定位，CGRP是中小型初级神经元的另一种神经肽标志物。与SP共同释放的CGRP增强了SP的突触后效应，从而调节伤害性信号传递。本研究展示了正常大鼠以及在三叉神经根切断术或在极间亚核（Vi）水平进行束切断术后，CGRP样免疫反应性（-ir）和SP-ir在下脑干中的分布。通过比较正常大鼠和去传入神经大鼠的结果，我们分析了三叉神经初级伤害感受器的中枢投射。CGRP免疫反应性（-ir）三叉神经初级纤维投射到同侧脊髓三叉神经核、主核（PrV）、三叉旁核（paraV）和孤束核外侧亚核（STN）的整个 rostrocaudal 范围。投射到脊髓三叉神经核、paraV和STN的三叉神经初级纤维也含有SP-ir。同侧三叉神经初级纤维是PrV、Vi和口侧亚核（Vo）内背内侧核中CGRP-ir终末的唯一来源。延髓背角（MDH）和Vo的外侧边缘接受来自同侧三叉神经初级纤维和其他神经元的汇聚CGRP-ir投射。舌咽神经和迷走神经初级纤维是向Vo和MDH投射CGRP-ir的候选来源，而背根轴突为MDH提供CGRP-ir终末。此外，穿过中线的对侧初级神经元似乎含有CGRP并终止于MDH。
