Department of Neuroscience and Pharmacology, the Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark.
Curr Pharm Des. 2013;19(24):4357-70. doi: 10.2174/1381612811319240004.
In this review we will first give a historical account of how the discovery of persistent inward currents (PICs) and plateau potentials changed the understanding of the operation and function of the "final common path", i.e. the motoneurons themselves. A major function of voltage-dependent PICs is to serve as an adjustable amplifier of classical synaptic inputs. The complex control of this, and other intrinsic properties, certainly adjusts the performance of the motoneurons to the needs of the behavioral settings. It has emerged that supraspinal facilitation, mainly by monoaminergic projections, is a prerequisite for the normal function of the PIC channels. When these pathways are interrupted following a spinal lesion the "gain" of the transmission across the motoneurons is reduced and this is likely to be an important explanation for the spinal shock. However, after a few weeks the "plateau properties" of the motoneurons return - now without descending monoaminergic control. This plasticity after spinal lesion is likely to contribute to the hyperreflexia (spasticity) seen after spinal lesions. We then review the current knowledge on PICs in other spinal (inter-)neurons. The monoaminergic systems seem to play a pivotal role in activating the spinal network generating the rhythm and basic motor pattern of locomotion and scratch - the spinal "central pattern generators" (CPGs). We give a short historical background of this research with a special emphasis on the importance of the descending monoaminergic systems.
在这篇综述中，我们首先将回顾持久内向电流 (PIC) 和平台电位的发现如何改变了对“最终共同途径”，即运动神经元本身的运作和功能的理解。电压依赖性 PIC 的主要功能是作为经典突触输入的可调放大器。这种复杂的控制，以及其他内在特性，肯定会根据行为环境的需要调整运动神经元的性能。已经出现的是，来自单胺能投射的上位促进作用是 PIC 通道正常功能的前提。当这些通路在脊髓损伤后中断时，运动神经元之间的“增益”降低，这很可能是脊髓休克的一个重要解释。然而，几周后，运动神经元的“平台特性”恢复——现在没有下行单胺能控制。这种脊髓损伤后的可塑性可能有助于解释脊髓损伤后的反射亢进（痉挛）。然后，我们回顾了其他脊髓（内）神经元中 PIC 的最新知识。单胺能系统似乎在激活产生运动和抓挠的节律和基本运动模式的脊髓网络中发挥关键作用——脊髓“中枢模式发生器”（CPG）。我们简要回顾了这项研究的历史背景，特别强调了下行单胺能系统的重要性。
