An excitatory GABAergic plexus in developing neocortical layer 1
An excitatory GABAergic plexus in developing neocortical layer 1
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DOI：
10.1152/jn.2000.84.1.428
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发表时间：
2000-07-01
影响因子：
2.5
通讯作者：
Kriegstein, AR
中科院分区：
文献类型：
--
作者：
Dammerman, RS;Flint, AC;Kriegstein, AR
发育中的啮齿类动物躯体感觉皮层的第1层含有密集的、短暂的GABA能纤维丛。从腹侧丘脑的齿状回（ZI）产生的轴突有助于该神经丛，第1层的内在GABA能细胞的轴突也是如此。这种早期出现的纤维丛的功能尚不清楚，但这些纤维的位置与大多数迁移后神经元的顶端树突接触。在这里，我们表明，电刺激层1的结果在GABA（A）介导的突触后电流（PSC）的锥体神经元。短杆菌肽穿孔斑片记录表明，GABA能第1层突触是兴奋性的，可以触发皮层神经元的动作电位。与电刺激相反，用谷氨酸激动剂激活内在层1神经元不能在锥体细胞中产生PSC。此外，在距离记录部位相对较远的距离处刺激第1层可以诱发反应。这些发现与广泛投射的皮层下通路的贡献一致，这是唯一描述的GABA能投射到新生儿皮层的通路。记录确定的新生儿incertocortical神经元揭示了一个活跃的细胞，表现出高频率的自发动作电位，并能够稳健地激活新生儿皮层神经元的人口。由于纤维丛被限制在第1层，这条途径提供了一个空间限制的兴奋性GABA能神经支配的锥体神经元的远端顶端树突在高峰期的皮质突触。
Layer 1 of the developing rodent somatosensory cortex contains a dense, transient GABAergic fiber plexus. Axons arising from the zona incerta (ZI) of the ventral thalamus contribute to this plexus, as do axons of intrinsic GABAergic cells of layer 1. The function of this early-appearing fiber plexus is not known, but these fibers are positioned to contact the apical dendrites of most postmigratory neurons. Here we show that electrical stimulation of layer 1 results in a GABA(A)-mediated postsynaptic current (PSC) in pyramidal neurons. Gramicidin perforated patch recording demonstrates that the GABAergic layer 1 synapse is excitatory and can trigger action potentials in cortical neurons. In contrast to electrical stimulation, activation of intrinsic layer 1 neurons with a glutamate agonist fails to produce PSCs in pyramidal cells. In addition, responses can be evoked by stimulation of layer 1 at relatively large distances from the recording site. These findings are consistent with a contribution of the widely projecting incertocortical pathway, the only described GABAergic projection to neonatal cortex. Recording of identified neonatal incertocortical neurons reveals a population of active cells that exhibit high frequencies of spontaneous action potentials and are capable of robustly activating neonatal cortical neurons. Because the fiber plexus is confined to layer 1, this pathway provides a spatially restricted excitatory GABAergic innervation of the distal apical dendrites of pyramidal neurons during the peak period of cortical synaptogenesis.