Lee R K, Eaton R C, Zottoli S J
Center for Neuroscience, University of Colorado, Boulder 80309-0334.
J Comp Neurol. 1993 Mar 22;329(4):539-56. doi: 10.1002/cne.903290409.
The hindbrain is evolutionarily conserved among diverse vertebrate phyla. In vertebrate embryos, the hindbrain is segmentally organized as a series of overt swellings known as rhombomeres. In the larval zebrafish Brachydanio rerio, conspicuous and identifiable reticulospinal neurons are positioned in the center of rhombomeres. Segmentally homologous reticulospinal neurons that share a range of morphological, developmental, and biochemical features occupy adjacent rhombomeres. We have recently shown that reticulospinal neurons of the zebrafish survive ontogeny without considerable morphological modification and we suggested that homologous neurons may share similar functions at different stages of development (Lee and Eaton: Journal of Comparative Neurology 304:34-52, 1991). The goldfish Carassius auratus, a related cyprinid, is especially suited for neurophysiological and behavioral studies. However, it is not yet known if the various reticulospinal neurons of zebrafish are generalizable to other species such as the goldfish. Therefore, we sought to examine the extent to which reticulospinal neurons of the zebrafish are also present in the adult goldfish. Analysis of 45 brains retrogradely labeled with horseradish peroxidase (HRP) from the spinal cord showed that reticulospinal neurons are arranged as a series of seven segments within the hindbrain; a regular interval of approximately 200 microns separates adjacent segments. Although the goldfish reticulospinal system has more neurons than the zebrafish, many reticulospinal neuron types continue to be identifiable. Moreover, comparisons of dendritic arborizations and axon paths between the two species showed that the morphology between various neuron types is virtually identical. The cross-taxonomic similarities between the reticulospinal systems of these related cyprinids make it possible to pursue functional considerations of segmentally homologous neurons in the goldfish hindbrain.
后脑在不同脊椎动物门类中在进化上是保守的。在脊椎动物胚胎中，后脑呈节段性组织，表现为一系列明显的膨出，即菱脑节。在斑马鱼幼体（短担尼鱼）中，明显且可识别的网状脊髓神经元位于菱脑节的中央。具有一系列形态、发育和生化特征的节段同源网状脊髓神经元占据相邻的菱脑节。我们最近发现，斑马鱼的网状脊髓神经元在个体发育过程中存活下来，且形态没有明显改变，我们认为同源神经元在发育的不同阶段可能具有相似的功能（Lee和Eaton：《比较神经学杂志》304:34 - 52，1991）。金鱼（鲫属）是一种相关的鲤科鱼类，特别适合进行神经生理学和行为学研究。然而，尚不清楚斑马鱼的各种网状脊髓神经元是否也适用于其他物种，如金鱼。因此，我们试图研究斑马鱼的网状脊髓神经元在成年金鱼中存在的程度。对45个用辣根过氧化物酶（HRP）从脊髓逆行标记的脑进行分析表明，网状脊髓神经元在后脑内排列成七个节段；相邻节段之间有大约200微米的规则间隔。虽然金鱼的网状脊髓系统比斑马鱼的神经元更多，但许多网状脊髓神经元类型仍然可以识别。此外，对这两个物种之间树突分支和轴突路径的比较表明，各种神经元类型之间的形态几乎相同。这些相关鲤科鱼类的网状脊髓系统之间的跨分类相似性使得研究金鱼后脑节段同源神经元的功能成为可能。
