Efficacy and connectivity of intracolumnar pairs of layer 2/3 pyramidal cells in the barrel cortex of juvenile rats
Efficacy and connectivity of intracolumnar pairs of layer 2/3 pyramidal cells in the barrel cortex of juvenile rats
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DOI：
10.1113/jphysiol.2006.105106
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发表时间：
2006-09-01
影响因子：
5.5
通讯作者：
Sakmann, Bert
中科院分区：
文献类型：
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作者：
Feldmeyer, Dirk;Luebke, Joachim;Sakmann, Bert
突触耦合层2/3（L2/3）的锥体神经元位于同一层4桶（“桶相关”）进行了研究，使用双全细胞电压记录在大鼠体感皮层急性切片。记录后重建充满生物细胞素的神经元。单一EPSP的起始潜伏期为1.1 ± 0.4ms，20-80%上升时间为0.7 ± 0.2ms，平均振幅为1.0 ± 0.7mV，衰减时间常数为15.7 ± 4.5ms。单一EPSP振幅随EPSP峰值增加而降低，为0.33 ± 0.18。突触前锥体细胞的AP爆发导致EPSP，在很宽的频率范围内（5-100 Hz），表现出幅度抑制。在解剖学上，第2/3层下半部分的桶相关的锥体细胞具有长的顶端树突，具有小的终末簇，而第2/3层上半部分的锥体细胞具有较短且通常更“不规则”形状的顶端树突，其在第1层中丰富地分支。由L2/3锥体细胞的轴突侧支与同一列中的突触后锥体细胞建立的假定兴奋性突触接触的数量在2和4之间变化，平均为2.8 +/- 0.7（n = 8对）。突触接触主要建立在从锥体细胞索马的平均几何距离为91 +/- 47 μ m的基底树突上。L2/3至L2/3连接形成了一个斑点状的神经支配域，包含2.8 mm的突触前轴突侧支，每μ m轴突具有0.3个终扣密度。在其主柱的颗粒上层内，单个L2/3锥体细胞建立了约900个终扣，这表明在第2/3层中的270个锥体细胞由单个锥体细胞支配。反过来，单个锥体细胞接收来自其他270个L2/3锥体细胞的突触输入。L2/3至L2/3连接的神经支配域几乎与L4至L2/3连接的神经支配域完全重叠。这表明，从层4到达的L2/3锥体细胞的同步前馈激励可能在层2/3中通过列内的反馈激励被潜在地放大，然后被中继到相邻列。
Synaptically coupled layer 2/3 (L2/3) pyramidal neurones located above the same layer 4 barrel ('barrel-related') were investigated using dual whole-cell voltage recordings in acute slices of rat somatosensory cortex. Recordings were followed by reconstructions of biocytin-filled neurones. The onset latency of unitary EPSPs was 1.1 +/- 0.4 ms, the 20-80% rise time was 0.7 +/- 0.2 ms, the average amplitude was 1.0 +/- 0.7 mV and the decay time constant was 15.7 +/- 4.5 ms. The coefficient of variation (c.v.) of unitary EPSP amplitudes decreased with increasing EPSP peak and was 0.33 +/- 0.18. Bursts of APs in the presynaptic pyramidal cell resulted in EPSPs that, over a wide range of frequencies (5-100 Hz), displayed amplitude depression. Anatomically the barrel-related pyramidal cells in the lower half of layer 2/3 have a long apical dendrite with a small terminal tuft, while pyramidal cells in the upper half of layer 2/3 have shorter and often more 'irregularly' shaped apical dendrites that branch profusely in layer 1. The number of putative excitatory synaptic contacts established by the axonal collaterals of a L2/3 pyramidal cell with a postsynaptic pyramidal cell in the same column varied between 2 and 4, with an average of 2.8 +/- 0.7 (n = 8 pairs). Synaptic contacts were established predominantly on the basal dendrites at a mean geometric distance of 91 +/- 47 mu m from the pyramidal cell soma. L2/3-to-L2/3 connections formed a blob-like innervation domain containing 2.8 mm of the presynaptic axon collaterals with a bouton density of 0.3 boutons per mu m axon. Within the supragranular layers of its home column a single L2/3 pyramidal cell established about 900 boutons suggesting that 270 pyramidal cells in layer 2/3 are innervated by an individual pyramidal cell. In turn, a single pyramidal cell received synaptic inputs from 270 other L2/3 pyramidal cells. The innervation domain of L2/3-to-L2/3 connections superimposes almost exactly with that of L4-to-L2/3 connections. This suggests that synchronous feed-forward excitation of L2/3 pyramidal cells arriving from layer 4 could be potentially amplified in layer 2/3 by feedback excitation within a column and then relayed to the neighbouring columns.