Multiple modes of action potential initiation and propagation in mitral cell primary dendrite
Multiple modes of action potential initiation and propagation in mitral cell primary dendrite
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DOI：
10.1152/jn.00057.2002
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发表时间：
2002-11-01
影响因子：
2.5
通讯作者：
Midtgaard, J
中科院分区：
文献类型：
--
作者：
Chen, WR;Shen, GY;Midtgaard, J
僧帽细胞初级树突在嗅球向轴突起始段传递远侧嗅神经输入中起重要作用。为了了解树突状细胞的活性特性是如何参与这种传输，我们结合了双索马和树突补丁记录与计算建模分析动作电位的启动和传播的初级树突。响应于去极化电流注入或远端嗅神经输入，快Na+动作电位记录沿着整个长度的初级树突状干。在弱到中等的嗅神经输入下，动作电位在索马附近开始，然后反向传播到初级树突。随着嗅神经输入的增加，起始部位突然转移到远端初级树突。多房室模型表明，这种突然转变的尖峰起始网站反映了一个独立的阈值机制在远端树突。当嗅神经的强兴奋与对僧帽细胞基底二级树突的强抑制配对时，在索马体处记录到小的快前电位，这表明动作电位起始于远端初级树突，但未能传播到索马体。当抑制减弱时，在树突记录位点经常观察到“双峰”，对应于索马的单个动作电位。模拟结果表明，在第一个树突棘向前传播的过程中，动作电位突然从树突中部跳到轴突棘起始点，使初级树突的近端部分不被这个初始树突棘兴奋。由于近端树突中的Na+电导未被激活，它们变得可用于支持诱发的躯体动作电位的反向传播以产生第二树突棘波。总之，空间分布的兴奋性和抑制性输入的平衡可以在四种不同的模式之间动态地切换二尖瓣细胞放电：具有反向传播的轴-体细胞启动，没有正向传播的树突启动，仅正向传播，或正向传播后反向传播。
The mitral cell primary dendrite plays an important role in transmitting distal olfactory nerve input from olfactory glomerulus to the soma-axon initial segment. To understand how dendritic active properties are involved in this transmission, we have combined dual soma and dendritic patch recordings with computational modeling to analyze action-potential initiation and propagation in the primary dendrite. In response to depolarizing current injection or distal olfactory nerve input, fast Na+ action potentials were recorded along the entire length of the primary dendritic trunk. With weak-to-moderate olfactory nerve input, an action potential was initiated near the soma and then back-propagated into the primary dendrite. As olfactory nerve input increased, the initiation site suddenly shifted to the distal primary dendrite. Multi-compartmental modeling indicated that this abrupt shift of the spike-initiation site reflected an independent thresholding mechanism in the distal dendrite. When strong olfactory nerve excitation was paired with strong inhibition to the mitral cell basal secondary dendrites, a small fast prepotential was recorded at the soma, which indicated that an action potential was initiated in the distal primary dendrite but failed to propagate to the soma. As the inhibition became weaker, a "double-spike" was often observed at the dendritic recording site, corresponding to a single action potential at the soma. Simulation demonstrated that, in the course of forward propagation of the first dendritic spike, the action potential suddenly jumps from the middle of the dendrite to the axonal spike-initiation site, leaving the proximal part of primary dendrite unexcited by this initial dendritic spike. As Na+ conductances in the proximal dendrite are not activated, they become available to support the back-propagation of the evoked somatic action potential to produce the second dendritic spike. In summary, the balance of spatially distributed excitatory and inhibitory inputs can dynamically switch the mitral cell firing among four different modes: axo-somatic initiation with back-propagation, dendritic initiation either with no forward propagation, forward propagation alone, or forward propagation followed by back-propagation.