Local neural circuit in the cerebral cortex

1.用细胞内染色结合Golgi样逆行标记法观察了大鼠初级运动皮层第III层锥体神经元与第V层皮质脊髓神经元和第VI层皮质丘脑神经元的联系。40个细胞内染色的第III层锥体神经元为规则尖峰型，表现出转氨酶免疫反应性，并在第II/III层和/或第V层发出局部分支的轴突侧支。其中9个进行了重建的形态学分析;15.2%或3.8%的重建神经元的轴突侧支静脉曲张分别与皮质脊髓或皮质丘脑神经元的树突并列。通过共聚焦激光扫描和电子显微镜，发现其中一些并置形成突触。这些发现表明，皮质脊髓神经元从皮层浅层接收信息的频率是皮质丘脑神经元的四倍。 关于我们 刺激第II/III层诱发V、VI层锥体神经元兴奋性突触后电位（EPSP）。在第V层锥体神经元诱发的EPSP表现出短而恒定的起始潜伏期，表明其单突触性质。而在第VI层锥体神经元诱发的EPSP大多数具有长潜伏期、双电刺激易化潜伏期，且可被NMDA受体阻断剂抑制，提示它们是多突触的，提示皮层浅层的信息可直接有效地传递到第V层的皮质脊髓神经元，从而对皮层运动输出产生重要影响。相反，皮质丘脑神经元被认为相对独立于或间接与浅层的信息处理有关.我们成功地通过感染腺病毒载体实现了皮质锥体细胞的Golgi染色样逆行显像，该腺病毒载体含有带有膜靶向信号的绿色荧光蛋白（GFP）表达系统.我们现在正在尝试克隆钙视网膜蛋白和小清蛋白的启动子区域，这是皮质GABA能中间神经元亚群的标记。通过使用启动子区域在转基因小鼠中特异性表达膜靶向GFP，以高尔基体染色方式标记中间神经元。少

1. Connections of layer III pyramidal neurons to corticospinal of layer V and corticothalamic neurons of layer VI in the rat primary motor cortex were examined in brain slices by combining intracellular staining with Golgi-like retrograde labeling of corticofugal neurons. Forty layer III pyramidal neurons stained intracellularly were of the regular-spiking type, showed immunoreactivity for glutaminase, and emitted axon collaterals arborizing locally in layers II/III and/or V. Nine of them were reconstructed for morphological analysis;15.2% or 3.8% of varicosities of axon collaterals of the reconstructed neurons were apposed to dendrites of corticospinal or corticothalamic neurons, respectively. By con-focal laser-scanning and electron microscopy, some of these appositions were revealed to make synapses. These findings suggest that corticospinal neurons receive information from the superficial cortical layers four times more frequently than corticothalamic neurons.The connections were f … More urther examined by intracellular recording of excitatory postsynaptic potential(EPSP)that were evoked in layer V and layer VI pyramidal neurons by stimulation of layer II/III. EPSPs evoked in layer V pyramidal neurons showed short and constant onset latencies, suggesting their monosynaptic nature. In contrast, most EPSPs evoked in layer VI pyramidal had long onset latencies, showed double-shock facilitation of onset latency, and were largely suppressed by an NMDA receptor blocker, implying that they were polysynaptic.The results suggest that information from the superficial cortical layers is transferred directly and efficiently to corticospinal neurons in layer V and there by exerts an important influence on cortical motor output. Corticothalamic neurons are, in contrast, considered relatively independent of, or indirectly related to, information processing of the superficial layers.2. We have succeeded in retrograde Golgi-stain-like visualization of cortical pyramidal cells by infection of adenovirus vector which contain the expression system of green fluorescent protein(GFP)attached with membrane-targetting signal.3. We are now trying the cloning of promoter regions of calretinin and parvalbumin, which are the marker for the subgroups of cortical GABAergic interneurons. The interneurons will be labeled in a Golgi-stain manner by specific expression of membrane-targetted GFP in transgenic mice using the promoter regions. Less