Reliable synaptic connections between pairs of excitatory layer 4 neurones within a single 'barrel' of developing rat somatosensory cortex
Reliable synaptic connections between pairs of excitatory layer 4 neurones within a single 'barrel' of developing rat somatosensory cortex
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DOI：
10.1111/j.1469-7793.1999.00169.x
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发表时间：
1999-11-15
影响因子：
5.5
通讯作者：
Sakmann, B
中科院分区：
文献类型：
--
作者：
Feldmeyer, D;Egger, V;Sakmann, B
1.双全细胞记录从对突触耦合兴奋性神经元的'桶场'在层（L）4在年轻（出生后第12-15天）大鼠体感皮层切片。大多数相互连接的兴奋性神经元是多刺的星状细胞，具有不对称的树突状分支，主要局限于一个单一的桶。其余为星星锥体细胞，顶端树突突出，终止于L2/3，未形成丛.在131对棘状L4神经元之间检查兴奋性突触连接。单个突触前动作电位诱发单一EPSP，峰值振幅为1.59 ± 1.51 mV（平均值± S.D），潜伏期为0.92 ± 0.35 ms，上升时间为1.53 ± 0.46 ms，衰减时间常数为17.8 ± 6.3 ms.在34-36 ℃下，变异系数（c. v.）单一EPSP振幅的百分比为0.37 ± 0.18，诱发EPSP失败的百分比为5.3 ± 7.8%。随着单一EPSP幅值的增加，c. v.和失败率降低。L4棘状神经元的突触后谷氨酸受体为AMPA和NMDA型。在-60 mV和1 mar Mg 2+存在下，NMDA受体对EPSP积分的贡献为39.3 +/-12.5%。在无Mg 2+溶液中，EPSC的NMDA受体/AMPA受体比率为0.86 +/- 0.64.5。由投射神经元与靶神经元建立的推定突触接触的数量在2到5之间变化，平均值为3.4 +/- 1.0（n = 11）。突触接触被专门发现在桶中的细胞对位于和优先位于二级到四级树突状分支。它们与索马的平均几何距离为68.8 +/- 37.4 μ m（范围，33.4-168.0 μ m）。突触接触数与EPSP平均波幅无显著相关性.结果表明，在L4桶皮质中，多刺神经元之间的突触传递很大程度上限于单个桶。连接是非常可靠的，可能是由于高的释放概率，并具有高的功效，因为多刺神经元的树突和轴突的紧凑结构。因此，桶内连接的功能是放大和分配传入丘脑活动的垂直方向的皮质柱。
1. Dual whole-cell recordings were made from pairs of synaptically coupled excitatory neurones in the 'barrel field' in layer (L)4 in slices of young (postnatal day 12-15) rat somatosensory cortex. The majority of interconnected excitatory neurones were spiny stellate cells with an asymmetrical dendritic arborisation largely confined to a single barrel. The remainder were star pyramidal cells with a prominent apical dendrite terminating in L2/3 without forming a tuft.2. Excitatory synaptic connections were examined between 131 pairs of spiny L4 neurones. Single presynaptic action potentials evoked unitary EPSPs with a peak amplitude of 1.59 +/- 1.51 mV (mean +/- S.D), a latency of 0.92 +/- 0.35 ms, a rise time of 1.53 +/- 0.46 ms and a decay time constant of 17.8 +/- 6.3 ms.3. At 34-36 degrees C, the coefficient of variation (c.v.) of the unitary EPSP amplitude was 0.37 +/- 0.18 and the percentage of failures to evoke an EPSP was 5.3 +/- 7.8%. The c.v. and failure rate decreased with increasing amplitude of the unitary EPSP.4. Postsynaptic glutamate receptors in spiny L4 neurones were of the AMPA and NMDA type. At -60 mV in the presence of 1 mar Mg2+, NMDA receptors contributed 39.3 +/- 12.5% to the EPSP integral. In Mg2+-free solution, the NMDA receptor/AMPA receptor ratio of the EPSC was 0.86 +/- 0.64.5. The number of putative synaptic contacts established by the projection neurone with the target neurone varied between two and five with a mean of 3.4 +/- 1.0 (n = 11). Synaptic contacts were exclusively found in the barrel in which the cell pair was located and were preferentially located on secondary to quarternary dendritic branches. Their mean geometric distance from the soma was 68.8 +/- 37.4 mu m (range, 33.4-168.0 mu m). The number of synaptic contacts and mean EPSP amplitude showed no significant correlation.6. The results suggest that in L4 of the barrel cortex synaptic transmission between spiny neurones is largely restricted to a single barrel. The connections are very reliable, probably due to a high release probability, and have a high efficacy because of the compact structure of the dendrites and axons of spiny neurones. Intrabarrel connections thus function to amplify and distribute the afferent thalamic activity in the vertical directions of a cortical column.