Department of Neuroanatomy, Institute of Anatomy and Cell Biology, University of Freiburg, D-79104 Freiburg, Germany.
Cereb Cortex. 2010 Sep;20(9):2043-54. doi: 10.1093/cercor/bhp267. Epub 2010 Jan 6.
The mammalian cortex exhibits a laminated structure that may underlie optimal synaptic connectivity and support temporally precise activation of neurons. In 'reeler' mice, the lack of the extracellular matrix protein Reelin leads to abnormal positioning of cortical neurons and disrupted layering. To address how these structural changes impact neuronal function, we combined electrophysiological and neuroanatomical techniques to investigate the synaptic activation of hippocampal mossy cells (MCs), the cell type that integrates the output of dentate gyrus granule cells (GCs). While somatodendritic domains of wild-type (WT) MCs were confined to the hilus, the somata and dendrites of reeler MCs were often found in the molecular layer, where the perforant path (PP) terminates. Most reeler MCs received aberrant monosynaptic excitatory input from the PP, whereas the disynaptic input to MCs via GCs was decreased and inhibition was increased. In contrast to the uniform disynaptic discharge of WT MCs, many reeler cells discharged with short, monosynaptic latencies, while others fired with long latencies over a broad temporal window in response to PP activation. Thus, disturbed lamination results in aberrant synaptic connectivity and altered timing of action potential generation. These results highlight the importance of a layered cortical structure for information processing.
哺乳动物皮层表现出分层结构，这可能是最佳突触连接的基础，并支持神经元的时间精确激活。在“reeler”小鼠中，细胞外基质蛋白 Reelin 的缺失导致皮层神经元的异常定位和分层的破坏。为了解这些结构变化如何影响神经元功能，我们结合电生理和神经解剖技术，研究了海马苔藓细胞（MCs）的突触激活，MCs 是整合齿状回颗粒细胞（GCs）输出的细胞类型。虽然野生型（WT）MCs 的体树突域局限于门区，但 reeler MCs 的胞体和树突经常出现在分子层，即穿通纤维（PP）终止的地方。大多数 reeler MCs 从 PP 接收异常的单突触兴奋性输入，而通过 GCs 对 MCs 的双突触输入减少，抑制增加。与 WT MCs 均匀的双突触放电相反，许多 reeler 细胞对 PP 激活的反应具有较短的单突触潜伏期，而其他细胞则在较宽的时间窗口内以长潜伏期放电。因此，分层紊乱导致异常的突触连接和动作电位产生时间的改变。这些结果强调了分层皮层结构对于信息处理的重要性。
