Ultrastructure of geniculocortical synaptic connections in the tree shrew striate cortex.
Ultrastructure of geniculocortical synaptic connections in the tree shrew striate cortex.
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DOI：
10.1002/cne.23907
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发表时间：
2016-04-15
期刊：
影响因子：
--
通讯作者：
Bickford ME
中科院分区：
文献类型：
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作者：
Familtsev D;Quiggins R;Masterson SP;Dang W;Slusarczyk AS;Petry HM;Bickford ME
为了确定丘脑皮质突触回路是否在不同的皮质区域之间存在差异，我们检查了树鼠纹状皮质膝状体皮质终末的超微结构，以便直接将这些终末的特征与枕叶皮质终末的特征进行比较(先前在同一物种的颞叶皮质中进行了检查)。树鼠被认为代表了早期原猴灵长类的原型，但它的独特之处在于纹状皮质IV层的亚胺优先对光开始(IVa)或偏移(IVb)做出反应。我们检查了通过示踪剂或病毒注射或抗2型囊泡谷氨酸抗体(VGLUT2)标记的这两个亚层的膝状体皮质输入。我们发现，第四层膝状体皮质终末及其突触后靶点明显大于枕皮质终末及其突触后靶点。此外，我们还发现，在每个亚层中，9-10%的膝状体皮质终末与GABA能中间神经元接触，而枕皮质终末未发现与任何中间神经元接触。此外，我们还发现，IVa和IVb的膝状体皮质终末大多含有树突，而枕皮质终末不含这些结构。最后，我们发现突触素和端脑素(TLCN，或细胞间黏附分子类型5，ICAM5)，一种与树突棘成熟有关的蛋白质，基本上不在纹状体皮质的膝状体皮质接受层中。综上所述，我们的结果提示纹状体和纹外区丘脑皮质通路的突触组织存在重大差异。将腺相关病毒注射入树鼠纹状体背外侧膝状体第一层，可诱导荧光蛋白TdTomato(紫色)在树鼠纹皮质Iva层表达。切片上还用抗2型囊泡谷氨酸转运蛋白(vGLUT2，绿色)的抗体进行了染色。比例=20(米。皮质层IIIc、IVb和V也被标明。
To determine whether thalamocortical synaptic circuits differ across cortical areas, we examined the ultrastructure of geniculocortical terminals in the tree shrew striate cortex in order to directly compare the characteristics of these terminals to that of pulvinocortical terminals (examined previously in the temporal cortex of the same species,). Tree shrews are considered to represent a prototype of early prosimian primates, but are unique in that sublaminae of striate cortex layer IV respond preferentially to light onset (IVa) or offset (IVb). We examined geniculocortical inputs to these two sublayers labeled by tracer or virus injections, or an antibody against the type 2 vesicular glutamate antibody (vGLUT2). We found that layer IV geniculocortical terminals, as well as their postsynaptic targets, were significantly larger than pulvinocortical terminals and their postsynaptic targets. In addition, we found that 9–10% of geniculocortical terminals in each sublamina contacted GABAergic interneurons, whereas pulvinocortical terminals were not found to contact any interneurons. Moreover, we found that the majority of geniculocortical terminals in both IVa and IVb contained dendritic protrusions, while pulvinocortical terminals do not contain these structures. Finally, we found that synaptopodin, a protein uniquely associated with the spine apparatus, and telencephalin (TLCN, or Intercellular Adhesion Molecule type 5, ICAM5), a protein associated with maturation of dendritic spines, are largely excluded from geniculocortical recipient layers of the striate cortex. Together, our results suggest major differences in the synaptic organization of thalamocortical pathways in striate and extrastriate areas. Injection of adenoassociated virus in layer 1 of the dorsal lateral geniculate nucleus induced the expression of the fluorescent protein TdTomato (purple) in layer IVa of the tree shrew striate cortex. The section was additionally stained with an antibody against the type 2 vesicular glutamate transporter (vGLUT2, green). Scale = 20 (m. Cortical layers IIIc, IVb and V are also indicated.