Connectivity of GABAergic calretinin-immunoreactive neurons in rat primary visual cortex
Connectivity of GABAergic calretinin-immunoreactive neurons in rat primary visual cortex
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DOI：
10.1093/cercor/9.7.683
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发表时间：
1999-10-01
期刊：
影响因子：
3.7
通讯作者：
Burkhalter, A
中科院分区：
文献类型：
--
作者：
Gonchar, Y;Burkhalter, A
在大鼠视觉皮层神经元中，对钙结合蛋白calretinin （CR+）有免疫反应的神经元构成了一个独特的家族，占γ -氨基丁酸（GABA）表达细胞的17%。然而，目前尚不清楚(i) CR是否仅在gaba能神经元中表达，（ii） CR+神经元如何被纳入大鼠视觉皮层的神经元回路。为了解决这些问题，我们研究了大鼠初级视觉皮层（17区）神经pil中CR+神经元与GABA（+）和GABA（-）元件的突触关系。所有CR+神经元都是非锥体细胞，树突光滑或稀疏，常呈串珠状。在所有CRC神经元中，56%位于1层和2/3层。在第2/3层，大多数CR+神经元呈双极状，具有垂直定向的树突。许多上升的树突分支到达第一层，在那里它们平行于脑膜表面。CR+轴突较细，在细胞体附近高度分支，常向第5层和第6层输送下行侧枝。双免疫荧光标记显示，94%的CR+细胞体在2/3层有GABA。电镜分析显示，所有CR+轴突末端均含有细长的囊泡，并形成对称的突触。包埋后染色显示98%的CR+末端为GABA（+）。在CR+神经元的体细胞和粗树突中也存在GABA免疫反应性，但许多细树突是GABA-。CR+体细胞、树突和轴突末端富集于线粒体。体细胞和粗CR+树突神经密集。2/3层CR+末端至少68%的目标是GABA(+)，其中大于或等于50%是其他CR+神经元。其余（32%）的CR+末端靶细胞是GABA-细胞的细树突。相反，在第5层和第6层，60%的CR+末端形成具有GABA-体细胞谱的突触。2/3层CR+神经元与gaba能神经元，特别是与CR+神经元的优先相互作用表明，这些细胞对同一层的抑制性神经元起抑制作用。通过这些相互作用，CR+细胞可以减少锥体细胞在2/3层、5层和6层的抑制，从而解除对一列神经元的抑制。
In rat Visual cortex neurons that are immunoreactive for the calcium binding protein calretinin (CR+) constitute a distinct family which accounts for 17% of gamma-aminobutyric acid (GABA) expressing cells. It is not clear, however, (i) whether CR is expressed exclusively in GABAergic neurons and (ii) how CR+ neurons are incorporated into neuronal circuits of rat visual cortex. To address these questions we studied synaptic relationships of CR+ neurons with GABA(+) and GABA(-) elements in the neuropil of rat primary Visual cortex (area 17). Ail CR+ neurons are nonpyramidal cells with smooth or sparsely spiny and often beaded dendrites. Of all CRC neurons, 56% are located in layers 1 and 2/3. In layer 2/3, most CR+ neurons are bipolar-shaped and have vertically oriented dendrites. Many ascending dendritic branches reach layer 1 where they run parallel to pial surface. CR+ axons are thin, highly branched near the cell body and often send descending collaterals to layers 5 and 6. Double immunofluorescence labeling revealed GABA in 94% of CR+ cell bodies in layer 2/3. Electron microscopic analysis shows that all CR+ axon terminals contain elongated vesicles and form symmetric synapses. Postembedding staining shows that 98% of CR+ terminals are GABA(+). GABA-immunoreactivity is also present in somata and thick dendrites of CR+ neurons but many thin dendrites are GABA-. CR+ somata, dendrites and axon terminals are enriched in mitochondria. Somata and thick CR+ dendrites are densely innervated. At least 68% of the targets of CR+ terminals in layer 2/3 are GABA(+) and greater than or equal to 50% of these are other CR+ neurons. The remainder (32%) of targets of CR+ terminals are thin dendrites of GABA- cells. In contrast, in layers 5 and 6, 60% of CR+ terminals form synapses with GABA- somatic profiles. The preferential interactions of layer 2/3 CR+ neurons with GABAergic neurons, and with CR+ neurons in particular, suggests that these cells play a role in the inhibition of inhibitory neurons of the same layer. Through these interactions CR+ cells may reduce inhibition of pyramidal cells in layers 2/3, 5 and 6 and thus disinhibit a column of neurons.