Active Action Potential Propagation But Not Initiation in Thalamic Interneuron Dendrites
Active Action Potential Propagation But Not Initiation in Thalamic Interneuron Dendrites
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DOI：
10.1523/jneurosci.4417-11.2011
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发表时间：
2011-12-14
影响因子：
5.3
通讯作者：
McCormick, David A.
中科院分区：
文献类型：
--
作者：
Casale, Amanda E.;McCormick, David A.
丘脑背外侧膝状核的抑制性中间神经元通过轴突和树突释放抑制性神经递质来调节丘脑皮质细胞的活性，以响应兴奋性输入。然而，从树突中释放的确切机制尚不清楚。最近的钙成像实验表明，钠基动作电位可以通过局部活动电导在树突中引起钙瞬态，使反向传播动作电位成为树突神经递质释放的候选。在这项研究中，我们使用高时空分辨率电压敏感染料成像来评估小鼠背外侧膝状核中间神经元对Na/K动作电位响应的树突电压偏移特征。我们发现，由体电流注射或局部突触刺激引发的序列或单一动作电位迅速而积极地反向传播到整个树突，并进入已知释放gaba能囊泡的细丝状树突附属物。在体电流注入或局部突触刺激下，动作电位总是首先出现在体细胞或近端树突中，并依靠电压门控钠和四乙基氯化铵敏感钾通道快速反向传播到树突乔木中。我们的研究结果表明，丘脑中间神经元树突整合了突触输入，这些输入很可能在轴突初始段启动动作电位，然后以高保真度反向传播到树突，导致轴突和树突隔室几乎同步释放GABA。
Inhibitory interneurons of the dorsal lateral geniculate nucleus of the thalamus modulate the activity of thalamocortical cells in response to excitatory input through the release of inhibitory neurotransmitter from both axons and dendrites. The exact mechanisms by which release can occur from dendrites are, however, not well understood. Recent experiments using calcium imaging have suggested that Na/K-based action potentials can evoke calcium transients in dendrites via local active conductances, making the backpropagating action potential a candidate for dendritic neurotransmitter release. In this study, we used high temporal and spatial resolution voltage-sensitive dye imaging to assess the characteristics of dendritic voltage deflections in response to Na/K action potentials in interneurons of the mouse dorsal lateral geniculate nucleus. We found that trains or single action potentials elicited by somatic current injection or local synaptic stimulation rapidly and actively backpropagated throughout the entire dendritic arbor and into the fine filiform dendritic appendages known to release GABAergic vesicles. Action potentials always appeared first in the soma or proximal dendrite in response to somatic current injection or local synaptic stimulation, and the rapid backpropagation into the dendritic arbor depended upon voltage-gated sodium and tetraethylammonium chloride-sensitive potassium channels. Our results indicate that thalamic interneuron dendrites integrate synaptic inputs that initiate action potentials, most likely in the axon initial segment, that then backpropagate with high fidelity into the dendrites, resulting in a nearly synchronous release of GABA from both axonal and dendritic compartments.