Local neural circuit in the cerebral cortex

1. 采用细胞内染色和高尔基样逆行标记相结合的方法，观察大鼠初级运动皮层第III层锥体神经元与第V层皮质脊髓和第VI层皮质丘脑神经元的连接。细胞内染色的40个III层锥体神经元为规则尖峰型，对谷氨酰胺酶具有免疫反应性，并在II/III和/或v层发出局部树突状的轴突侧枝，其中9个被重建用于形态学分析，重建神经元的轴突侧枝变异分别与皮质脊髓或皮质丘脑神经元的树突相对应，分别占15.2%和3.8%。通过激光共焦扫描和电子显微镜观察，发现其中的一些位点形成突触。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。通过细胞内记录刺激第II/III层锥体神经元引起的第V层和第VI层的兴奋性突触后电位（EPSP），进一步研究了这种联系。V层锥体神经元诱发的EPSPs潜伏期短且持续，提示其单突触性。与之相反，在第六层锥体中诱发的epsp大多具有较长的起始潜伏期，表现出双激促进的起始潜伏期，并在很大程度上被NMDA受体阻滞剂抑制，表明它们是多突触的。结果表明，来自皮层表层的信息直接有效地传递到V层的皮质脊髓神经元，并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。我们利用含有绿色荧光蛋白（GFP）表达系统的腺病毒载体感染皮质锥形细胞，成功地实现了逆行高尔基染色样可视化。我们目前正在尝试克隆calretinin和parvalbumin的启动子区域，这是皮质gaba能中间神经元亚群的标志。通过在转基因小鼠中使用启动子区域特异性表达膜靶向GFP，以高尔基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