Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, 188-1, 2-Ga, Samdeok-Dong, Jung-Gu, Daegu, 700-412, South Korea.
Research Division, Korea Brain Research Institute, Daegu, 700-010, South Korea.
Brain Struct Funct. 2018 Jun;223(5):2323-2334. doi: 10.1007/s00429-018-1636-y. Epub 2018 Feb 23.
To provide information on the glutamatergic synapses on the trigeminal motoneurons, which may be important for understanding the mechanism of control of jaw movements, we investigated the distribution of vesicular glutamate transporter (VGLUT)1-immunopositive (+) and VGLUT2 + axon terminals (boutons) on the rat jaw-closing (JC) and jaw-opening (JO) motoneurons, and their morphological determinants of synaptic strength by retrograde tracing, electron microscopic immunohistochemistry, and quantitative ultrastructural analysis. We found that (1) the large majority of VGLUT + boutons on JC and JO motoneurons were VGLUT2+, (2) the density of VGLUT1 + boutons terminating on JC motoneurons was significantly higher than that on JO motoneurons, (3) the density of VGLUT1 + boutons terminating on non-primary dendrites of JC motoneurons was significantly higher than that on somata or primary dendrites, whereas the density of VGLUT2 + boutons was not significantly different between JC and JO motoneurons and among various compartments of the postsynaptic neurons, and (4) the bouton volume, mitochondrial volume, and active zone area of the VGLUT1 + boutons forming synapses on JC motoneurons were significantly bigger than those of VGLUT2 + boutons. These findings suggest that JC and JO motoneurons receive glutamatergic input primarily from VGLUT2-expressing intrinsic neurons (premotoneurons), and may be controlled differently by neurons in the trigeminal mesencephalic nucleus and by glutamatergic premotoneurons.
为了提供关于三叉运动神经元上的谷氨酸能突触的信息，这对于理解下颌运动控制的机制可能很重要，我们通过逆行追踪、电子显微镜免疫组织化学和定量超微结构分析，研究了囊泡谷氨酸转运体（VGLUT）1 免疫阳性（+）和 VGLUT2 + 轴突末梢（终末）在大鼠闭口（JC）和开口（JO）运动神经元上的分布，以及它们的突触强度的形态学决定因素。我们发现：（1）JC 和 JO 运动神经元上的大多数 VGLUT + 终末都是 VGLUT2 +；（2）终止于 JC 运动神经元上的 VGLUT1 + 终末的密度明显高于终止于 JO 运动神经元上的密度；（3）终止于 JC 运动神经元非初级树突上的 VGLUT1 + 终末的密度明显高于终止于胞体或初级树突上的密度，而终止于 JC 和 JO 运动神经元以及突触后神经元各种隔室上的 VGLUT2 + 终末的密度没有明显差异；（4）形成 JC 运动神经元突触的 VGLUT1 + 终末的终末体体积、线粒体体积和活性区面积明显大于 VGLUT2 + 终末。这些发现表明，JC 和 JO 运动神经元主要接收来自表达 VGLUT2 的内在神经元（前运动神经元）的谷氨酸能输入，并且可能由三叉神经中脑核内的神经元和谷氨酸能前运动神经元以不同的方式控制。
