Mechanisms of rhythm generation in a spinal locomotor network deprived of crossed connections: The lamprey hemicord
Mechanisms of rhythm generation in a spinal locomotor network deprived of crossed connections: The lamprey hemicord
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DOI：
10.1523/jneurosci.2301-04.2005
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发表时间：
2005-01-26
影响因子：
5.3
通讯作者：
Grillner, S
中科院分区：
文献类型：
--
作者：
Cangiano, L;Grillner, S
协调七鳃鳗运动的脊髓网络作为模型系统，可以使用分离的脊髓来阐明连接性和细胞机制。运动爆发活动通过相互抑制在节段的左侧和右侧之间交替。我们最近表明，半段中的突发生成本身不需要抑制机制。本研究的重点是运动网络的半节段爆发生成组件的内在运作。半索的短暂电刺激（0.3 秒）会在中高频运动范围内引起持久（> 2 分钟）的爆发（2 - 15 Hz）。布特释放是一种全有或全无的现象，需要在兴奋性中间神经元群体内进行刺激和谷氨酸能传递的阈值强度，轴突延伸到多个节段。比赛期间发生的爆发频率随活动而逐渐降低，随后是持续 > 20 分钟的缓慢恢复过程。单个运动神经元、兴奋性中间神经元和抑制性中间神经元的细胞内记录表明，运动发作通常伴随着明显的去极化。膜电位振荡和尖峰与腹侧根 (VR) 爆发同相发生。活动运动神经元和中间神经元每次 VR 爆发都会发射一个尖峰，轴突记录也证实了这一点。因此，完整脊髓中相对半节之间的相互抑制不仅确保左右交替并降低运动频率，而且促进网络神经元每个周期从单一动作电位向多个动作电位的转变。
The spinal network coordinating locomotion in the lamprey serves as a model system, in which it has been possible to elucidate connectivity and cellular mechanisms using the isolated spinal cord. Locomotor burst activity alternates between the left and right side of a segment through reciprocal inhibition. We have recently shown that the burst generation itself in a hemisegment does not require inhibitory mechanisms. The focus of this study is the intrinsic operation of this hemisegmental burst- generating component of the locomotor network.Brief electrical stimulation ( 0.3 s) of the hemicord evokes long- lasting bouts ( > 2 min) of bursts ( 2 - 15 Hz) in the mid to high- frequency range of locomotion. Bout release is an all- or- none phenomenon requiring a threshold intensity of stimulation and glutamatergic transmission within a population of excitatory interneurons, with axons extending over several segments. The progressive activity-dependent decrease in burst frequency that takes place during a bout is followed by a slow recovery process lasting > 20 min. Intracellular recordings of single motoneurons, excitatory interneurons, and inhibitory interneurons show that locomotor bouts, in general, are accompanied by a marked depolarization. Membrane potential oscillations and spikes occur in phase with the ventral root ( VR) bursts. Active motoneurons and interneurons fire one spike per VR burst, as also confirmed by axonal recordings. Thus, the reciprocal inhibition between opposite hemisegments in the intact cord not only ensures left - right alternation and lowers the locomotor frequency but also promotes a shift from single to multiple action potentials per cycle in network neurons.