Physiologisches Institut, Universität Bern, CH-3012 Bern, Switzerland.
J Neurosci. 2010 Sep 29;30(39):13031-44. doi: 10.1523/JNEUROSCI.2254-10.2010.
Layer 6 (L6) pyramidal neurons are the only neocortical pyramidal cell type whose apical dendrite terminates in layer 4 rather than layer 1. Like layer 5 pyramidal neurons, they participate in a feedback loop with the thalamus and project to other cortical areas. Despite their unique location in the cortical microcircuit, synaptic integration in dendrites of L6 neurons has never been investigated. Given that all other neocortical pyramidal neurons perform active integration of synaptic inputs via local dendritic spike generation, we were interested to establish the apical dendritic properties of L6 pyramidal neurons. We measured active and passive properties of the apical dendrites of L6 pyramidal neurons in the somatosensory region of rat cortical slices using dual patch-clamp recordings from somata and dendrites and calcium imaging. We found that L6 pyramidal neurons share many fundamental dendritic properties with other neocortical pyramidal neurons, including the generation of local dendritic spikes under the control of dendritic inhibition, voltage-dependent support of backpropagating action potentials, timing-dependent dendritic integration, distally located I(h) channels, frequency-dependent Ca(2+) spike activation, and NMDA spike electrogenesis in the distal apical dendrite. The results suggest that L6 pyramidal neurons integrate synaptic inputs in layer 4 similar to the way other neocortical pyramidal neurons integrate input to layer 1. Thus, L6 pyramidal neurons can perform a similar associational task operating on inputs arriving at the granular and subgranular layers.
第 6 层(L6)锥体神经元是唯一一种其顶树突终止于第 4 层而不是第 1 层的新皮质锥体细胞类型。与第 5 层锥体神经元一样,它们参与与丘脑的反馈回路,并投射到其他皮质区域。尽管它们在皮质微电路中的位置独特,但 L6 神经元树突中的突触整合从未被研究过。鉴于所有其他新皮质锥体神经元通过局部树突棘产生来执行突触输入的主动整合,我们有兴趣确定 L6 锥体神经元的顶树突特性。我们使用来自体细胞和树突的双膜片钳记录以及钙成像,在大鼠皮质切片的体感区域测量 L6 锥体神经元的顶树突的主动和被动特性。我们发现,L6 锥体神经元与其他新皮质锥体神经元具有许多基本的树突特性,包括在树突抑制控制下产生局部树突棘、电压依赖性支持逆行动作电位、时变依赖性树突整合、位于远端的 I(h)通道、频率依赖性 Ca(2+)棘激活和 NMDA 棘电发生在远端顶树突。结果表明,L6 锥体神经元在第 4 层整合突触输入的方式与其他新皮质锥体神经元在第 1 层整合输入的方式相似。因此,L6 锥体神经元可以执行类似的联想任务,对到达颗粒层和亚颗粒层的输入进行操作。
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