Local neural circuit in the cerebral cortex

1.用细胞内染色结合高尔基体样逆行标记法，在脑片上观察了大鼠初级运动皮质内第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。细胞内染色的40个III层锥体神经元为规则棘型，谷氨酰胺酶免疫反应阳性，并发出局部分布在II/III层和/或V层的轴突侧支，其中9个进行了形态分析，重建后的神经元轴索侧支曲张分别有15.2%和3.8%与皮质脊髓或皮质丘脑神经元的树突相对。通过激光共聚焦扫描和电子显微镜观察，发现其中一些对位可以形成突触。这些发现表明，皮质脊髓神经元从皮质浅层接收信息的频率是皮质丘脑神经元的四倍。这些联系是f…进一步通过细胞内记录刺激II/III层的V层和VI层锥体神经元诱发的兴奋性突触后电位(EPSP)，发现V层锥体神经元诱发的EPSP潜伏期短而恒定，提示其具有单突触的性质。相比之下，在第VI层锥体诱发的大多数EPSP具有较长的起效潜伏期，表现出起效潜伏期的双电击易化，并被NMDA受体阻滞剂抑制，这表明它们是多突触。结果表明，来自皮质浅层的信息直接有效地传递到第V层的皮质脊髓神经元，从而对皮质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地与浅层的信息处理有关。通过携带带有膜靶向信号的绿色荧光蛋白(GFP)表达系统的腺病毒载体，成功地逆行显示了皮质锥体细胞的高尔基染色样染色。我们现在正在尝试克隆钙视黄素和小白蛋白的启动子区域，这是皮质GABA能中间神经元亚群的标志。中间神经元将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来进行高尔基染色标记。较少

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