Lustig D G, Herrick J L, Keifer J
Department of Anatomy & Structural Biology, University of South Dakota School of Medicine, Vermillion 57069, USA.
J Comp Neurol. 1998 Jul 13;396(4):521-30. doi: 10.1002/(sici)1096-9861(19980713)396:4<521::aid-cne8>3.0.co;2-3.
The rat and turtle differ markedly in major structural features of the corticocerebellorubrospinal circuitry. Although both species have a well-developed cerebellorubrospinal system, they differ in that a direct cerebral cortical input to the red nucleus is present only in the rat. The aim of the present study was to compare features of the soma and dendritic morphology of rubrospinal neurons that receive cortical input, as in rats, with those that do not, as in turtles. Intracellular Lucifer Yellow injections of neurons retrogradely labeled with Fast Blue in the rat or activity-dependent sulforhodamine-labeled neurons in the turtle were used to fill rubrospinal neurons in 150-200-microm-thick fixed sections. Images of filled neurons were imported into a computer to analyze quantitatively soma and dendritic morphology. The results show that rubrospinal soma size is slightly larger in the rat than in the turtle. However, analysis of the dendritic morphology, including total dendritic length, length of primary, secondary, and tertiary dendritic branches, and a Scholl analysis of dendritic branch intersections across concentric rings, demonstrated no significant differences between the two species. These findings suggest that the basic dendritic morphology of rubrospinal neurons may have been established early in phylogeny, preceding the evolution of cortical inputs. Alternatively, similar dendritic morphologies may have arisen due to the presence of other synapses in the turtle that occupy the sites of the cortical input in the rat. This comparative approach provides insights into the information processing capabilities of cortically versus subcortically controlled motor systems.
大鼠和龟在皮质-小脑-红核-脊髓神经回路的主要结构特征上存在显著差异。尽管这两个物种都有发育良好的小脑-红核-脊髓系统，但它们的不同之处在于，只有大鼠存在大脑皮质对红核的直接输入。本研究的目的是比较接受皮质输入的红核脊髓神经元（如大鼠）与不接受皮质输入的红核脊髓神经元（如龟）的胞体和树突形态特征。在大鼠中，对用快蓝逆行标记的神经元进行细胞内注射路西法黄；在龟中，对活动依赖性的磺基罗丹明标记的神经元进行注射，以此来填充150 - 200微米厚的固定切片中的红核脊髓神经元。将填充后的神经元图像导入计算机，以定量分析胞体和树突形态。结果表明，大鼠红核脊髓神经元的胞体大小略大于龟。然而，对树突形态的分析，包括总树突长度、一级、二级和三级树突分支的长度，以及对穿过同心环的树突分支交叉点的肖尔分析，表明这两个物种之间没有显著差异。这些发现表明，红核脊髓神经元的基本树突形态可能在系统发育早期就已确立，早于皮质输入的进化。或者，由于龟中存在其他占据大鼠皮质输入位点的突触，可能产生了相似的树突形态。这种比较方法为深入了解皮质控制与皮质下控制的运动系统的信息处理能力提供了线索。
