康奈尔大学的研究人员利用最新科技研究幼小斑马鱼的脊索，结果在脊索中发现了一种出乎意料的功能组织类型。
根据这篇发表于3月1日Nature的文章，研究人员发现幼小斑马鱼脊索中沿背腹轴方面的神经元位置，与斑马鱼游动速度所引起的神经元活化，有直接的关连性。
电生理学和活体影像之研究显示，游动速度较快时，靠近斑马鱼背部的运动神经元和激发性中间神经元会被活化，而斑马鱼游动速度较慢时，则会使位置更靠腹部、朝向脊索下半部分的神经元活化。脊索功能的分布，能使斑马鱼游动时效率更高。
鱼类到两栖类和哺乳动物在演化过程中，都保留了早期的脊索发育，所以这种类型的组织可能也存在于其它动物中。这项研究结果有助于治疗脊髓受损或帕金森氏症患者。
(资料来源 : Bio.com)
部分英文原文
Nature 446, 71-75 (1 March 2007) | doi:10.1038/nature05588; Received 16 November 2006; Accepted 10 January 2007
A topographic map of recruitment in spinal cord
David L. McLean1, Jingyi Fan2, Shin-ichi Higashijima3, Melina E. Hale2 and Joseph R. Fetcho1
Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA
Department of Organismal Biology and Anatomy, University of Chicago, Chicago, Illinois 60637, USA
National Institutes of Natural Sciences, Okazaki Institute for Integrative Bioscience and National Institute for Physiological Sciences, Myodaiji Okazaki, Aichi 444-8787, Japan
Correspondence to: Joseph R. Fetcho1 Correspondence and requests for materials should be addressed to J.R.F. (Email: jrf49@cornell.edu).
Animals move over a range of speeds by using rhythmic networks of neurons located in the spinal cord1, 2, 3, 4, 5, 6. Here we use electrophysiology and in vivo imaging in larval zebrafish (Danio rerio) to reveal a systematic relationship between the location of a spinal neuron and the minimal swimming frequency at which the neuron is active. Ventral motor neurons and excitatory interneurons are rhythmically active at the lowest swimming frequencies, with increasingly more dorsal excitatory neurons engaged as swimming frequency rises. Inhibitory interneurons follow the opposite pattern. These inverted patterns of recruitment are independent of cell soma size among interneurons, but may be partly explained by concomitant dorso-ventral gradients in input resistance. Laser ablations of ventral, but not dorsal, excitatory interneurons perturb slow movements, supporting a behavioural role for the topography. Our results reveal an unexpected pattern of organization within zebrafish spinal cord that underlies the production of movements of varying speeds.
