Paik Sang Kyoo, Choi Seung Ki, Lee Jong Wook, Kim Tae Heon, Ahn Dong Kuk, Yoshida Atsushi, Kim Yun Sook, Bae Yong Chul
Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea.
Anat Cell Biol. 2010 Dec;43(4):340-6. doi: 10.5115/acb.2010.43.4.340. Epub 2010 Dec 31.
Ultrastructural parameters related to synaptic release and their correlation with synaptic connectivity were analyzed in the low-threshold mechanoreceptive vibrissa afferent boutons in laminae III and IV of the trigeminal caudal nucleus (Vc). Rapidly adapting vibrissa afferents were intra-axonally labeled, and quantitative ultrastructural analyses with serial sections were performed on the labeled boutons and their presynaptic endings (p-endings). The volume of the labeled boutons was widely distributed from small to large ones (0.8~12.3 µm(3)), whereas the p-endings were small and uniform in size. The volume of the labeled boutons was positively correlated with the ultrastructural parameters such as mitochondrial volume (correlation coefficient, r=0.96), active zone area (r=0.82) and apposed surface area (r=0.79). Vesicle density (r=-0.18) showed little correlation to the volume of labeled boutons, suggesting that the total vesicle number of a bouton is proportional to its volume. In addition, the bouton volume was positively correlated with the number of p-endings (r=0.52) and with the number of dendrites postsynaptic to the labeled bouton (r=0.83). These findings suggest that low-threshold mechanoreception conveyed through vibrissa afferents is processed in a bouton size-dependent manner in the Vc, which may contribute to the sensory-motor function of laminae III/IV in Vc.
对三叉神经尾侧核（Vc）第III和IV层中低阈值机械感受性触须传入终扣的与突触释放相关的超微结构参数及其与突触连接性的相关性进行了分析。对快速适应的触须传入纤维进行轴突内标记，并对标记的终扣及其突触前终末（p终末）进行连续切片的定量超微结构分析。标记终扣的体积分布广泛，从小到大都有（0.8~12.3 µm(3)），而p终末较小且大小均匀。标记终扣的体积与线粒体体积（相关系数，r=0.96）、活性区面积（r=0.82）和贴合表面积（r=0.79）等超微结构参数呈正相关。囊泡密度（r=-0.18）与标记终扣的体积相关性很小，表明终扣的囊泡总数与其体积成正比。此外，终扣体积与p终末的数量（r=0.52）以及与标记终扣突触后树突的数量（r=0.83）呈正相关。这些发现表明，通过触须传入纤维传递的低阈值机械感受在Vc中以终扣大小依赖的方式进行处理，这可能有助于Vc中第III/IV层的感觉运动功能。
