Systematic Shifts in the Balance of Excitation and Inhibition Coordinate the Activity of Axial Motor Pools at Different Speeds of Locomotion
Systematic Shifts in the Balance of Excitation and Inhibition Coordinate the Activity of Axial Motor Pools at Different Speeds of Locomotion
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DOI：
10.1523/jneurosci.0514-14.2014
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发表时间：
2014-10-15
影响因子：
5.3
通讯作者：
McLean, David L.
中科院分区：
文献类型：
--
作者：
Kishore, Sandeep;Bagnall, Martha W.;McLean, David L.
一个新兴的共识，从轴和肢体网络的研究是，不同的前运动人口所需的不同速度的运动。一个重要但尚未解决的问题是为什么会发生这种情况。在这里，我们进行电压钳记录从轴向运动神经元在幼斑马鱼在“虚构”游泳测试的想法，轴向运动神经元的生物物理特性的系统差异与差异调谐的重量和时间的突触驱动器，这将有助于解释premotor人口的转变。我们发现，游泳速度的增加伴随着兴奋的增加，优先于较低输入阻力（Rin）的运动神经元，而抑制则随着速度的增加而均匀地增加，无论Rin如何。此外，虽然随着速度的增加，池内的节奏兴奋性驱动的时间变得尖锐，但与Rin相关的抑制的主要来源发生了变化。在低速下，反相抑制在整个池中较大。然而，随着游泳速度的加快，抑制与局部运动活动同步增加，特别是在较高的Rin运动神经元中。因此，除了与Rin和速度相关的兴奋的重量和时间的系统差异外，不同抑制源的平衡也存在速度依赖性变化，这在更易兴奋的运动池中最为明显。我们的结论是，突触驱动差异调谐到运动神经元的生物物理特性，并认为，运动前电路的差异存在，以简化运动速度变化过程中脊髓运动池内的活动协调。
An emerging consensus from studies of axial and limb networks is that different premotor populations are required for different speeds of locomotion. An important but unresolved issue is why this occurs. Here, we perform voltage-clamp recordings from axial motoneurons in larval zebrafish during "fictive" swimming to test the idea that systematic differences in the biophysical properties of axial motoneurons are associated with differential tuning in the weight and timing of synaptic drive, which would help explain premotor population shifts. We find that increases in swimming speed are accompanied by increases in excitation preferentially to lower input resistance (Rin) motoneurons, whereas inhibition uniformly increases with speed to all motoneurons regardless of Rin. Additionally, while the timing of rhythmic excitatory drive sharpens within the pool as speed increases, there are shifts in the dominant source of inhibition related to Rin. At slow speeds, anti-phase inhibition is larger throughout the pool. However, as swimming speeds up, inhibition arriving in-phase with local motor activity increases, particularly in higher Rin motoneurons. Thus, in addition to systematic differences in the weight and timing of excitation related to Rin and speed, there are also speed-dependent shifts in the balance of different sources of inhibition, which is most obvious in more excitable motor pools. We conclude that synaptic drive is differentially tuned to the biophysical properties of motoneurons and argue that differences in premotor circuits exist to simplify the coordination of activity within spinal motor pools during changes in locomotor speed.