Relative location of inhibitory synapses and persistent inward currents determines the magnitude and mode of synaptic amplification in motoneurons
Relative location of inhibitory synapses and persistent inward currents determines the magnitude and mode of synaptic amplification in motoneurons
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DOI：
10.1152/jn.00718.2007
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发表时间：
2008-02-01
影响因子：
2.5
通讯作者：
Rose, P. Ken
中科院分区：
文献类型：
--
作者：
Bui, Tuan V.;Grande, Giovanbattista;Rose, P. Ken
在某些运动神经元中，部分介导持续性内向电流（PIC）的L-型Ca 2+通道被估计排列在树突中50- 200 μ m长的离散区域中，中心距索马100 - 400 μ m。由于这种非均匀分布，运动神经元的突触输入和这些通道之间的相互作用可能会根据突触的分布而变化。例如，已观察到来自Renshaw细胞的> 93%的突触位于距离运动神经元的细胞体65至470 μ m处。我们的目标是评估Renshaw细胞突触是否分布在更有效地控制L型Ca 2+通道激活的位置。使用房室模型的运动神经元分布在100 μ m长的热点中心100至400 μ m远离索马的L-型钙通道，我们比较了抑制性突触的四种分布产生的抑制：近端，远端，均匀，和一个基于运动神经元上的Renshaw细胞突触的位置。无论突触是紧张性激活还是瞬时激活，在L型Ca 2+通道存在下，根据Renshaw细胞突触分布分布的抑制性突触产生最大的抑制电流。抑制性突触在PIC存在下的特定分布的有效性取决于它们使PIC下的通道失活的能力，这不仅受到突触和通道之间的叠加的影响，而且还受到远离体细胞电压钳的距离的影响。
In some motoneurons, L-type Ca2+ channels that partly mediate persistent inward currents (PICs) have been estimated to be arranged in 50- to 200-mu m-long discrete regions in the dendrites, centered 100 to 400 mu m from the soma. As a consequence of this nonuniform distribution, the interaction between synaptic inputs to motoneurons and these channels may vary according to the distribution of the synapses. For instance, > 93% of synapses from Renshaw cells have been observed to be located 65 to 470 mu m away from the cell body of motoneurons. Our goal was to assess whether Renshaw cell synapses are distributed in a position to more effectively control the activation of the L-type Ca2+ channels. Using compartmental models of motoneurons with L-type Ca2+ channels distributed in 100-mu m-long hot spots centered 100 to 400 mu m away from the soma, we compared the inhibition generated by four distributions of inhibitory synapses: proximal, distal, uniform, and one based on the location of Renshaw cell synapses on motoneurons. Regardless of whether the synapses were activated tonically or transiently, in the presence of L-type Ca2+ channels, inhibitory synapses distributed according to the Renshaw cell synapse distribution generate the largest inhibitory currents. The effectiveness of a particular distribution of inhibitory synapses in the presence of PICs depends on their ability to deactivate the channels underlying PICs, which is influenced not only by the superposition between synapses and channels, but also by the distance away from the somatic voltage clamp.