Department of Anatomy, Histology and Embryology, Medical University of Sofia, Bulgaria.
Department of Anatomy, Histology and Embryology, Medical University of Sofia, Bulgaria.
Acta Histochem. 2019 May;121(4):383-391. doi: 10.1016/j.acthis.2019.02.009. Epub 2019 Mar 4.
The claustrum is a bilateral subcortical nucleus situated between the insular cortex and the striatum in the brain of all mammals. It consists of two embryologically distinct subdivisions - dorsal and ventral claustrum. The claustrum has high connectivity with various areas of the cortex, subcortical and allocortical structures. It has long been suggested that the various claustral connections have different types of synaptic contacts at the claustral neurons. However, to the best of our knowledge, the literature data on the ultrastructural organization of the different types of synaptic contacts in the dorsal claustrum are very few. Therefore, the aim of our study was to observe and describe the synaptic organization of the dorsal claustrum in the cat. We used a total of 10 adult male cats and conducted an ultrastructural study under a transmission electron microscope as per established protocol. We described a multitude of dendritic spines, which were subdivided into two types - with and without foot processes. Based on the size and shape of the terminal boutons, the quantity and distribution of vesicles and the characteristic features of the active synaptic zone, we described six types of synaptic boutons, most of which formed asymmetrical synaptic contacts. Furthermore, we reported the presence of axo-dendritic, axo-somatic, dendro-dendritic and axo-axonal synapses. The former two likely represent the morphological substrate of the corticoclaustral pathway, while the remaining two types have the ultrastructural features of inhibitory synapses, likely forming a local inhibitory circuit in the claustrum. In conclusion, the present study shares new information about the neuropil of the claustrum and proposes a systematic classification of the types of synaptic boutons and contacts observed in the dorsal claustrum of the cat, thus supporting its key and complex role as a structure integrating various information within the brain.
屏状核是一种位于大脑的双侧皮质下核，位于脑岛皮质和纹状体之间。它由两个胚胎上不同的部分组成 - 背侧和腹侧屏状核。屏状核与皮质、皮质下和外皮质的各种区域具有高度的连接。长期以来，人们一直认为各种屏状核连接在屏状核神经元上具有不同类型的突触接触。然而，据我们所知，关于背侧屏状核不同类型突触接触的超微结构组织的文献数据非常少。因此，我们的研究目的是观察和描述猫的背侧屏状核的突触组织。我们总共使用了 10 只成年雄性猫，并按照既定方案在透射电子显微镜下进行了超微结构研究。我们描述了多种树突棘，这些树突棘可分为两种类型 - 有足突和无足突。根据终末小球的大小和形状、囊泡的数量和分布以及活性突触区的特征，我们描述了六种类型的突触小球，其中大多数形成不对称的突触接触。此外，我们还报告了轴突-树突、轴突-体、树突-树突和轴突-轴突突触的存在。前两者可能代表皮质-屏状核途径的形态学基础，而其余两种类型具有抑制性突触的超微结构特征，可能在屏状核中形成局部抑制性回路。总之，本研究提供了关于屏状核神经胶质的新信息，并提出了一种系统的分类方法，用于对猫背侧屏状核中观察到的突触小球和接触类型进行分类，从而支持其作为整合大脑内各种信息的关键和复杂结构的作用。
