Jankowska E, Riddell J S, Szabo-Läckberg Z, Hammar I
Department of Physiology, University of Göteborg, Sweden.
J Comp Neurol. 1993 Nov 15;337(3):518-28. doi: 10.1002/cne.903370312.
The morphology of 12 sacral interneurones with peripheral input from group II muscle afferents was analyzed after intracellular injection of horseradish peroxidase (HRP). The neurones were located in Rexed's laminae III-V overlying the pudendal (Onuf's) motor nucleus. The interneurones had medium sized elongated somata and dendrites projecting radially. All of the interneurones were funicular neurones and fell into two categories depending on whether their axons ran within the dorsal part of the lateral funiculus (DLF; n = 7) or within the ventral funiculus, or the ventral part of the lateral funiculus (VF or VLF; n = 4). The latter were located more rostrally. Within the DLF similar proportions of stem axons and secondary axonal branches descended and ascended. Within the VF and VLF all of the axons ascended. Collaterals of axons running in the DLF arborized primarily within the dorsal horn and the intermediate zone; none were found to approach the motor nuclei. In contrast, collaterals of axons running in the VF/VLF arborized in both the intermediate zone and the ventral horn and passed close to the motor nuclei. We conclude that sacral interneurones with group II input are morphologically nonhomogenous and that only those located most rostrally might have direct actions upon motoneurones. Both the axonal projections and the input (from group II but not from group I muscle afferents and from skin afferents) of sacral interneurones indicate that they are homologous to dorsal horn group II interneurones in the midlumbar segments. They appear, however, to form part of more local neuronal networks than their midlumbar counterparts.
在对12个接受来自II类肌传入纤维外周输入的骶段中间神经元进行辣根过氧化物酶（HRP）细胞内注射后，分析了它们的形态。这些神经元位于阴部（奥努夫）运动核上方的雷克斯德III - V层。中间神经元具有中等大小的细长胞体，树突呈放射状伸出。所有中间神经元都是索状神经元，根据其轴突是在外侧索的背侧部分（DLF；n = 7）内运行，还是在腹侧索或外侧索的腹侧部分（VF或VLF；n = 4）内运行，可分为两类。后者位于更靠前的位置。在DLF内，主干轴突和次级轴突分支下降和上升的比例相似。在VF和VLF内，所有轴突都上升。在DLF中运行的轴突侧支主要在背角和中间带形成分支；未发现有侧支接近运动核。相比之下，在VF/VLF中运行的轴突侧支在中间带和腹角都有分支，并靠近运动核。我们得出结论，接受II类输入的骶段中间神经元在形态上是不均一的，只有那些位于最靠前位置的神经元可能对运动神经元有直接作用。骶段中间神经元的轴突投射和输入（来自II类而非I类肌传入纤维以及皮肤传入纤维）均表明它们与腰段中部背角的II类中间神经元同源。然而，它们似乎比腰段中部的对应神经元形成了更局部的神经元网络的一部分。
