Bras H, Cavallari P, Jankowska E, Kubin L
Department of Physiology, University of Göteborg, Sweden.
J Comp Neurol. 1989 Dec 1;290(1):1-15. doi: 10.1002/cne.902900102.
The morphology of midlumbar interneurones with peripheral input from group II muscle afferents was analysed after intracellular injection of horseradish peroxidase (HRP). Twenty-three interneurones were stained intrasomatically and five others intra-axonally. The majority (10 of 13) of interneurones located in lamina VII (intermediate zone and ventral horn interneurones) were found to project ipsilaterally. They had medium-sized somata and dendrites projecting radially over a distance of more than 1 mm. All of these neurones had axons that projected caudally within the ventral part of the lateral funiculus or in the lateral part of the ventral funiculus, although four had in addition an ascending secondary axonal branch. Numerous axon collaterals were given off from these axons, both before and after they left the grey matter. The collaterals arborized within laminae VII, VIII, and IX, where they covered the area of several motor nuclei. Intra-axonal labelling of five neurones with similar input and axon trajectories revealed several axon collaterals given off between the cell body and the terminal projection areas in L7 or S1 segments. Only three of the labelled interneurones located in lamina VII and displaying the same kind of input had axons with different destinations; their axons crossed to the opposite side of the spinal cord and ascended within the contralateral ventral funiculus. These were large neurones with extensive dendritic trees, which had fairly thick axons with initial axon collaterals that branched primarily ipsilaterally (within laminae V-VIII). Interneurones located in lamina V and in the bordering parts of laminae IV and VI (dorsal horn interneurones; n = 10) constituted a very nonhomogenous population. They projected either ipsilaterally or contralaterally and had either ascending or descending axons running in either the lateral or ventral funiculi. Generally, dorsal horn interneurones had cell bodies smaller than those of intermediate zone and ventral horn interneurones, and their dendrites extended less extensively and less uniformly around the soma. Their initial axon collaterals branched primarily in the dorsal horn, or in lamina VII, but not in or close to the motor nuclei. Our results support the conclusions of previous physiological studies that the intermediate zone and ventral horn midlumbar interneurones with group II input and that project to motor nuclei have collateral actions on other interneurones in the L4-L6 segments, and that dorsal horn interneurones do not project to motoneurones, but have as their targets other interneurones or ascending cells.(ABSTRACT TRUNCATED AT 400 WORDS)
在对辣根过氧化物酶（HRP）进行细胞内注射后，分析了具有来自II类肌肉传入纤维外周输入的腰髓中部中间神经元的形态。23个中间神经元通过胞内染色，另外5个通过轴突内染色。发现位于VII层（中间带和腹角中间神经元）的大多数中间神经元（13个中的10个）向同侧投射。它们具有中等大小的胞体，树突呈放射状延伸超过1毫米。所有这些神经元都有轴突，这些轴突在外侧索的腹侧部分或腹侧索的外侧部分向尾侧投射，尽管有4个神经元还具有一个上升的二级轴突分支。这些轴突在离开灰质之前和之后都发出许多轴突侧支。侧支在VII、VIII和IX层内形成分支，覆盖了几个运动核的区域。对5个具有相似输入和轴突轨迹的神经元进行轴突内标记，发现它们在细胞体与L7或S1节段的终末投射区域之间发出了几个轴突侧支。位于VII层且具有相同类型输入的仅3个标记中间神经元的轴突有不同的去向；它们的轴突交叉到脊髓的对侧，并在对侧腹侧索内上升。这些是具有广泛树突树的大神经元，其轴突相当粗，初始轴突侧支主要在同侧（V - VIII层内）分支。位于V层以及IV和VI层的相邻部分（背角中间神经元；n = 10）的中间神经元构成了一个非常不均一的群体。它们向同侧或对侧投射，轴突在外侧索或腹侧索中上升或下降。一般来说，背角中间神经元的胞体比中间带和腹角中间神经元的胞体小，并且它们的树突在胞体周围的延伸范围较小且不太均匀。它们的初始轴突侧支主要在背角或VII层内分支，但不在运动核内或其附近分支。我们的结果支持了先前生理学研究的结论，即具有II类输入并投射到运动核的腰髓中部中间带和腹角中间神经元对L4 - L6节段的其他中间神经元具有侧支作用，并且背角中间神经元不投射到运动神经元，而是以其他中间神经元或上升细胞为靶点。（摘要截断于400字）
