Fast and slow locomotor burst generation in the hemispinal cord of the lamprey
Fast and slow locomotor burst generation in the hemispinal cord of the lamprey
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DOI：
10.1152/jn.01100.2002
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发表时间：
2003-06-01
影响因子：
2.5
通讯作者：
Grillner, S
中科院分区：
文献类型：
--
作者：
Cangiano, L;Grillner, S
脊椎动物运动中的一个基本问题是，是否存在能够为每组肌肉协同者产生有节奏输出的不同脊髓网络。在包括七鳃鳗在内的许多脊椎动物中，已经声称爆发活性取决于拮抗剂之间的相互抑制。这个问题是解决在孤立的七鳃鳗脊髓中，每个肌节的左侧和右侧显示有节奏的交替活动。我们将脊髓沿中线沿着切开，并测试是否可以在半索中与完整脊髓中一样用浴缸应用的D-谷氨酸或N-甲基-D-天冬氨酸（NMDA）或通过短暂的电刺激来诱导节律性运动活动。三种方法均观察到腹根间协调的快速节律性爆发（2-12 Hz）。此外，为了逐渐减少交叉的甘氨酸能抑制，实施了跨越中线的轴突的渐进式手术损伤。这导致爆发频率逐渐增加，将快半弦节律[ 6.6 +/- 1.7（SD）Hz]与完整脊髓中的虚构游泳（2.4 +/- 0.7 Hz）牢固联系起来。同侧甘氨酸能抑制不需要的hemicord突发模式的产生，这表明兴奋性mammatergic神经元之间的相互作用足以产生单侧突发模式。在NMDA中，也遇到了频率低得多（0.1-0.4 Hz）的爆发活动，这需要NMDA受体的电压依赖性，而不是快节奏。因此，游泳是由成对的单侧爆发产生网络产生的，这些网络具有相互抑制的连接，不仅确保左/右交替，而且还下调频率。
A fundamental question in vertebrate locomotion is whether distinct spinal networks exist that are capable of generating rhythmic output for each group of muscle synergists. In many vertebrates including the lamprey, it has been claimed that burst activity depends on reciprocal inhibition between antagonists. This question was addressed in the isolated lamprey spinal cord in which the left and right sides of each myotome display rhythmic alternating activity. We sectioned the spinal cord along the midline and tested whether rhythmic motor activity could be induced in the hemicord with bath-applied D-glutamate or N-methyl-D-aspartate (NMDA) as in the intact spinal cord or by brief trains of electrical stimuli. Fast rhythmic bursting (2-12 Hz), coordinated across ventral roots, was observed with all three methods. Furthermore, to diminish gradually the crossed glycinergic inhibition, a progressive surgical lesioning of axons crossing the midline was implemented. This resulted in a gradual increase in burst frequency, linking firmly the fast hemicord rhythm [ 6.6 +/- 1.7 (SD) Hz] to fictive swimming in the intact cord (2.4 +/- 0.7 Hz). Ipsilateral glycinergic inhibition was not required for the hemicord burst pattern generation, suggesting that an interaction between excitatory glutamatergic neurons suffices to produce the unilateral burst pattern. In NMDA, burst activity at a much lower rate (0.1-0.4 Hz) was also encountered, which required the voltage-dependent properties of NMDA receptors in contrast to the fast rhythm. Swimming is thus produced by pairs of unilateral burst generating networks with reciprocal inhibitory connections that not only ensure left/right alternation but also downregulate frequency.