Núñez-Abades P A, He F, Barrionuevo G, Cameron W E
Department of Behavioral Neuroscience, University of Pittsburgh, Pennsylvania 15260.
J Comp Neurol. 1994 Jan 15;339(3):401-20. doi: 10.1002/cne.903390308.
The aim of this study is to describe the postnatal change in dendritic morphology of those motoneurons in the hypoglossal nucleus that innervate the genioglossus muscle. Forty genioglossal (GG) motoneurons from four age groups (1-2, 5-6, 13-15, and 19-30 postnatal days) were labeled by intracellular injection of neurobiotin in an in vitro slice preparation of the rat brainstem and were reconstructed in three-dimensional space. The number of primary dendrites per GG motoneuron was approximately 6 and remained unchanged with age. The development of these motoneurons from birth to 13-15 days was characterized by a simplification of the dendritic tree involving a decrease in the number of terminal endings and dendritic branches. Motoneurons lost their 6th-8th order branches, in parallel with an elongation of their terminal dendritic branches maintaining the same combined dendritic length. The elongation of terminal branches was attributed to both longitudinal growth and the apparent lengthening caused by resorption of distal branches. The elimination of dendritic branches tended to increase the symmetry of the tree, as revealed by topological analysis. Later, between 13-15 days and 19-30 days, there was a reelaboration of the dendritic arborization returning to a configuration similar to that found in the newborn. The length of terminal branches was shorter at 19-30 days, while the length of preterminal branches did not change, suggesting that the proliferation of branches at 19-30 days takes place in the intermediate parts of terminal branches. The three-dimensional distribution of dendrites was analyzed by dividing space into six equal volumes (hexants). This analysis revealed that GG motoneurons have major components of their dendritic tree oriented in the lateral, medial, and dorsal hexants. Further two-dimensional polar analysis (consisting of eight sectors) revealed a reconfiguration of the tree from birth up to 5-6 days involving resorption of dendrites in the dorsal, dorsomedial, and medial sectors and growth in the lateral sector. Later in development (between 13-15 days and 19-30 days), there was growth in all sectors, but of a greater magnitude in the dorsomedial, medial, and dorsolateral sectors.
本研究的目的是描述支配颏舌肌的舌下神经核运动神经元树突形态的出生后变化。在大鼠脑干的体外脑片制备中，通过细胞内注射神经生物素标记了来自四个年龄组（出生后1 - 2天、5 - 6天、13 - 15天和19 - 30天）的40个颏舌肌（GG）运动神经元，并在三维空间中进行重建。每个GG运动神经元的初级树突数量约为6个，且不随年龄变化。这些运动神经元从出生到13 - 15天的发育特征是树突简化，表现为终末分支和树突分支数量减少。运动神经元失去其第6 - 8级分支，同时其终末树突分支伸长，保持相同的总树突长度。终末分支的伸长归因于纵向生长以及远端分支吸收导致的明显延长。拓扑分析表明，树突分支的消除倾向于增加树的对称性。之后，在13 - 15天至19 - 30天之间，树突分支发生重新构建，恢复到类似于新生儿的构型。19 - 30天时终末分支较短，而终末前分支长度不变，这表明19 - 30天时分支的增殖发生在终末分支的中间部分。通过将空间划分为六个相等体积（卦限）来分析树突的三维分布。该分析表明，GG运动神经元树突树的主要部分朝向外侧、内侧和背侧卦限。进一步的二维极坐标分析（由八个扇区组成）表明，从出生到5 - 6天，树突树发生重新构型，涉及背侧、背内侧和内侧扇区树突的吸收以及外侧扇区的生长。在发育后期（13 - 15天至19 - 30天之间），所有扇区都有生长，但背内侧、内侧和背外侧扇区的生长幅度更大。
