MORPHOLOGICAL VARIABILITY, SEGMENTAL RELATIONSHIPS, AND FUNCTIONAL-ROLE OF A CLASS OF COMMISSURAL INTERNEURONS IN THE SPINAL-CORD OF GOLDFISH
MORPHOLOGICAL VARIABILITY, SEGMENTAL RELATIONSHIPS, AND FUNCTIONAL-ROLE OF A CLASS OF COMMISSURAL INTERNEURONS IN THE SPINAL-CORD OF GOLDFISH
复制标题
DOI：
10.1002/cne.902990303
复制
发表时间：
1990-09-15
影响因子：
2.5
通讯作者：
FETCHO, JR
中科院分区：
文献类型：
--
作者：
FETCHO, JR
作为了解金鱼节段轴向肌肉的脊髓控制的一部分，通过细胞内记录和染色研究了与毛特纳轴突（m -轴突）电张力偶联的脊髓中间神经元，以检查它们的形态、节段关系和功能作用。先前的研究表明，这些细胞可能介导交叉抑制，在逃避弯曲到另一侧时阻止身体一侧运动神经元的兴奋。同时来自m轴突、与其相连的互交中间神经元和一个假定的初级运动神经元的细胞内记录表明：(1)中间神经元在对侧运动神经元中产生单突触的、依赖Cl的ipsp；(2)中间神经元负责m细胞网络中的短潜伏期、交叉脊髓抑制；(3)每个突触后细胞上有多个中间神经元终止。中间神经元的整体重建表明，它们形成了一个相当均匀的形态学类细胞。每一个都是单极的，有一个轴突穿过脊髓，然后通常分成一个短而细的上升分支和一个粗而长的下降分支。邻近的中间神经元有重叠的终端乔木，这与生理学数据一致，表明中间神经元收敛到相同的突触后细胞。中间神经元与腹根界定的体段关系不大。它们的轴突通常跨越节段边界，末端通常占据两个相邻节段的部分。因此，这些细胞的功能单位可能不是一个节段或一组完整的节段，而是只包括两个相邻节段的部分。像这样的中间神经元的存在表明躯干肌肉组织的明显外周分割不一定反映在控制这些片段的神经元组织中。考虑到通过下行通路激活重叠的、连续重复的中间神经元阵列的一些功能特征，可以得出这样的结论：m轴突的高传导速度和抑制性中间神经元轴突的大尺寸和短纵向范围促进了强烈的、短暂的抑制，这适合于产生一个快速向一侧弯曲的逃逸转弯。
As part of an attempt to understand the spinal control of the segmented axial musculature in goldfish, commissural spinal interneurons that are electrotonically coupled to the Mauthner axon (M-axon) were studied with intracellular recording and staining to examine their morphology, segmental relationships, and functional role. Prior studies suggested that these cells might mediate the crossed inhibition that blocks excitation of motoneurons on one side of the body during an escape bend to the opposite side. Simultaneous intracellular recordings from a M-axon, a commissural interneuron coupled to it, and a presumed primary motoneuron show that: (1) the interneurons produce monosynaptic, Cl--dependent IPSPs in contralateral motoneurons, (2) the interneurons are responsible for the short latency, crossed spinal inhibition in the M-cell network, and (3) more than one interneuron terminates on each postsynaptic cell. Reconstructions of interneurons from wholemounts show that they form a fairly homogeneous morphological class of cells. Each one is unipolar, with an axon that crosses the cord and then usually bifurcates into a short, thin ascending branch and a thicker, longer descending one. Neighboring interneurons have overlapping terminal arbors consistent with the physiological data showing convergence of interneurons onto the same postsynaptic cell. The interneurons showed little relationship with body segments as defined by ventral roots. Their axons usually straddled segmental boundaries, with terminals typically occupying parts of two adjacent segments. Thus the functional unit of these cells is probably not a segment or a complete group of segments, but instead includes only parts of two adjacent segments. The presence of interneurons like these suggests that the overt peripheral segmentation of trunk musculature is not necessarily reflected in the organization of neurons that control those segments. A consideration of some functional characteristics of the activation of overlapping, serially repeated arrays of interneurons by descending pathways leads to the conclusion that the high conduction velocity of the M-axon, and the large size and short longitudinal extent of the axons of the inhibitory interneurons promote a strong, brief inhibition that is appropriate for the production of an escape turn that has a rapid bend to one side.