Hultborn Hans, Brownstone Robert B, Toth Tibor I, Gossard Jean-Pierre
Department of Medical Physiology, Panum Institute, University of Copenhagen, Copenhagen DK-2200, Denmark.
Prog Brain Res. 2004;143:77-95. doi: 10.1016/s0079-6123(03)43008-2.
This chapter summarizes a number of factors that control the "input-output" function across the motoneurons (MNs) comprising a single spinal motor nucleus. The main focus is on intrinsic properties of individual MNs that can be controlled by neuromodulators. These include: (1) amplification of the synaptic input at the cell's dendritic level by voltage-gated, persistent inward currents (plateau potentials); and (2) transduction of the net synaptic excitation into a frequency code (the MN's stimulus current-spike frequency relation) at the cell's soma/initial segment. Two other aspects of the synaptic control of MNs, which may affect their input-output gain, are also discussed. They include the hypotheses that: (1) a non-uniform distribution of synaptic effects to low- and high-threshold motor units causes a change in recruitment gain; and (2) recurrent inhibition, via motor axon collaterals and Renshaw cells, functions as a variable gain regulator of MN discharge.
本章总结了一些控制单个脊髓运动核中运动神经元（MNs）“输入-输出”功能的因素。主要关注点在于可由神经调质控制的单个MNs的内在特性。这些特性包括：（1）通过电压门控的持续性内向电流（平台电位）在细胞树突水平对突触输入进行放大；以及（2）在细胞体/起始段将净突触兴奋转化为频率编码（MN的刺激电流-放电频率关系）。还讨论了MNs突触控制的另外两个方面，它们可能会影响其输入-输出增益。这包括以下假设：（1）对低阈值和高阈值运动单位的突触效应分布不均会导致募集增益发生变化；以及（2）通过运动轴突侧支和闰绍细胞产生的回返抑制作为MN放电的可变增益调节器发挥作用。
