Metcalfe W K, Mendelson B, Kimmel C B
J Comp Neurol. 1986 Sep 8;251(2):147-59. doi: 10.1002/cne.902510202.
We have examined the morphology of identified reticulospinal neurons in larval zebrafish by retrogradely labeling them with horseradish peroxidase. We described the morphology of 27 different types of reticulospinal neurons found in the hindbrain 5 days after fertilization. Nineteen of these types are present as single identified neurons on each side of the brain; the others are present as pairs or small groups of cells. The hindbrain reticulospinal neurons are present in seven bilateral clusters that are spaced periodically along the neuraxis. Each cluster contains two to five different types of reticulospinal neurons. Cells with similar morphological features are found in adjacent clusters. By considering cell position within the cluster and axon pathway, nearly all of the cells can be assigned to one of about seven serially repeated classes. Independent morphological features of the cells support the same classification. We propose that the clusters represent hindbrain segments and that the neurons of the same class that are present in the different clusters are segmental homologues. Assuming that this series evolved by successive duplications and divergence of the primitive segments, we have analyzed the changes that may have occurred during the evolution of each new segment. Changes between ipsilaterally and contralaterally projecting axons may have occurred several times during the evolution of the series. In addition, cells may have been added or deleted.
我们通过用辣根过氧化物酶逆行标记已鉴定的斑马鱼幼体中脑网状脊髓神经元，研究了它们的形态。我们描述了受精后5天在后脑中发现的27种不同类型的网状脊髓神经元的形态。其中19种类型在脑的每一侧各有一个已鉴定的单个神经元；其他类型则以成对或小细胞群的形式存在。后脑网状脊髓神经元存在于七个双侧细胞簇中，这些细胞簇沿神经轴周期性分布。每个细胞簇包含两到五种不同类型的网状脊髓神经元。在相邻的细胞簇中发现具有相似形态特征的细胞。通过考虑细胞在细胞簇中的位置和轴突路径，几乎所有细胞都可以归入大约七个连续重复的类别之一。细胞的独立形态特征支持相同的分类。我们提出这些细胞簇代表后脑节段，并且不同细胞簇中存在的同一类神经元是节段同源物。假设这个系列是通过原始节段的连续复制和分化进化而来的，我们分析了每个新节段进化过程中可能发生的变化。在这个系列的进化过程中，同侧和对侧投射轴突之间的变化可能发生了几次。此外，细胞可能被添加或删除。
