Reconfiguration of a vertebrate motor network: Specific neuron recruitment and context-dependent synaptic plasticity
Reconfiguration of a vertebrate motor network: Specific neuron recruitment and context-dependent synaptic plasticity
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DOI：
10.1523/jneurosci.3694-07.2007
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发表时间：
2007-11-07
影响因子：
5.3
通讯作者：
Soffe, Stephen R.
中科院分区：
文献类型：
--
作者：
Li, Wen-Chang;Sautois, Bart;Soffe, Stephen R.
运动网络通常会产生几种相关的输出模式或步态，其中各个神经元可以在模式之间共享或招募。我们研究如何重新配置脊椎动物的运动网络，以产生第二个有节奏的运动模式，定义的详细模式的神经元招聘和随之而来的变化的机制，节奏的产生。刚孵化的非洲爪蟾蝌蚪如果被触摸就会游泳，但当被握住时，会做出更慢、更强、更挣扎的动作。在静止的蝌蚪中，皮肤上的短暂电流脉冲会引发游泳，而40 Hz的脉冲会产生挣扎。在挣扎过程中活跃的神经元类别是使用在40 Hz皮肤刺激期间来自后脑和脊髓神经元的全细胞贴片记录来定义的。一些运动神经元和抑制性中间神经元在游泳和挣扎中都很活跃，但在挣扎过程中，更多的神经元在这些类别中被招募。此外，与以前的研究相比，我们描述了两种新的兴奋性中间神经元，特别是在挣扎过程中招募，并定义其属性和突触连接。然后，我们通过构建一个包含这些新神经元的网络模型来探索产生挣扎的机制。以及新的神经元类的招聘，我们表明，重新配置的运动网络的挣扎中央模式发生器（CPG）揭示了一个上下文相关的突触抑制相互抑制：结果增加抑制神经元放电频率在挣扎。这提供了一种可能的机制，在游泳CPG中看不到爆发终止。相互抑制中抑郁的直接证明证实了Brown（1911）关于运动节律发生的假设的一个关键要素。
Motor networks typically generate several related output patterns or gaits where individual neurons may be shared or recruited between patterns. We investigate how a vertebrate locomotor network is reconfigured to produce a second rhythmic motor pattern, defining the detailed pattern of neuronal recruitment and consequent changes in the mechanism for rhythm generation. Hatchling Xenopus tadpoles swim if touched, but when held make slower, stronger, struggling movements. In immobilized tadpoles, a brief current pulse to the skin initiates swimming, whereas 40 Hz pulses produce struggling. The classes of neurons active during struggling are defined using whole-cell patch recordings from hindbrain and spinal cord neurons during 40 Hz stimulation of the skin. Some motoneurons and inhibitory interneurons are active in both swimming and struggling, but more neurons are recruited within these classes during struggling. In addition, and in contrast to a previous study, we describe two new classes of excitatory interneuron specifically recruited during struggling and define their properties and synaptic connections. We then explore mechanisms that generate struggling by building a network model incorporating these new neurons. As well as the recruitment of new neuron classes, we show that reconfiguration of the locomotor network to the struggling central pattern generator (CPG) reveals a context-dependent synaptic depression of reciprocal inhibition: the result of increased inhibitory neuron firing frequency during struggling. This provides one possible mechanism for burst termination not seen in the swimming CPG. The direct demonstration of depression in reciprocal inhibition confirms a key element of Brown's (1911) hypothesis for locomotor rhythmogenesis.