Kim Yun Sook, Paik Sang Kyoo, Cho Yi Sul, Shin Ho Seob, Bae Jin Young, Moritani Masayuki, Yoshida Atsushi, Ahn Dong Kuk, Valtschanoff Juli, Hwang Se Jin, Moon Cheil, Bae Yong Chul
Department of Oral Anatomy and Neurobiology, BK21, School of Dentistry, Kyungpook National University, Daegu 700-412, Korea.
J Comp Neurol. 2008 Feb 1;506(4):627-39. doi: 10.1002/cne.21544.
Trigeminal primary afferents expressing P2X(3) receptor are involved in the transmission of orofacial nociceptive information. However, little is known about their central projection pattern and ultrastructural features within the trigeminal brainstem sensory nuclei (TBSN). Here we use multiple immunofluorescence and electron microscopy to characterize the P2X(3)-immunopositive (+) neurons in the trigeminal ganglion and describe the distribution and synaptic organization of their central terminals within the rat TBSN, including nuclei principalis (Vp), oralis (Vo), interpolaris (Vi), and caudalis (Vc). In the trigeminal ganglion, P2X(3) immunoreactivity was mainly in small and medium-sized somata, but also frequently in large somata. Although most P2X(3) (+) somata costained for the nonpeptidergic marker IB4, few costained for the peptidergic marker substance P. Most P2X(3) (+) fibers in the sensory root of trigeminal ganglion (92.9%) were unmyelinated, whereas the rest were small myelinated. In the TBSN, P2X(3) immunoreactivity was dispersed in the rostral TBSN but was dense in the superficial laminae of Vc, especially in the inner lamina II. The P2X(3) (+) terminals contained numerous clear, round vesicles and sparse large, dense-core vesicles. Typically, they were presynaptic to one or two dendritic shafts and also frequently postsynaptic to axonal endings, containing pleomorphic vesicles. Such P2X(3) (+) terminals, showing glomerular shape and complex synaptic relationships, and those exhibiting axoaxonic contacts, were more frequently seen in Vp than in any other TBSN. These results suggest that orofacial nociceptive information may be transmitted via P2X(3) (+) afferents to all TBSN and that it may be processed differently in different TBSN.
表达P2X(3)受体的三叉神经初级传入纤维参与口面部伤害性信息的传递。然而，关于它们在三叉神经脑干感觉核（TBSN）内的中枢投射模式和超微结构特征却知之甚少。在此，我们运用多重免疫荧光和电子显微镜技术来表征三叉神经节中P2X(3)免疫阳性（+）神经元，并描述其在大鼠TBSN内中枢终末的分布及突触组织，包括三叉神经脑桥核（Vp）、三叉神经中脑核（Vo）、三叉神经脊束核中间亚核（Vi）和三叉神经脊束核尾侧亚核（Vc）。在三叉神经节中，P2X(3)免疫反应性主要存在于中小型神经元胞体中，但也常见于大型神经元胞体。尽管大多数P2X(3)（+）胞体与非肽能标记物IB4共染色，但很少与肽能标记物P物质共染色。三叉神经节感觉根中大多数P2X(3)（+）纤维（92.9%）是无髓鞘的，其余为小的有髓鞘纤维。在TBSN中，P2X(3)免疫反应性在TBSN头端呈散在分布，但在Vc的浅层，尤其是在内侧II层中密集。P2X(3)（+）终末含有大量清亮的圆形小泡和稀疏的大型致密核心小泡。通常，它们与一两个树突干形成突触前联系，并且也经常与含有多形性小泡的轴突终末形成突触后联系。这种呈小球状且具有复杂突触关系的P2X(3)（+）终末以及那些表现出轴-轴突触联系的终末，在Vp中比在其他任何TBSN中更常见。这些结果表明，口面部伤害性信息可能通过P2X(3)（+）传入纤维传递至所有TBSN，并且在不同的TBSN中可能会有不同的处理方式。
