Rubio-Garrido P, Pérez-de-Manzo F, Clascá F
Department of Anatomy and Neuroscience, Autonoma University School of Medicine, Avenida Arzobispo Morcillo s/n, Madrid, E-28029, Spain.
Neuroscience. 2007 Oct 12;149(1):242-50. doi: 10.1016/j.neuroscience.2007.07.036. Epub 2007 Aug 1.
The thalamus contains two main populations of projection neurons that selectively innervate different elements of the cortical microcircuit: the well-known "specific" or "core" (C-type) cells that innervate cortical layer IV, and, the "matrix" (M-type) cells that innervate layer I. Observations in different mammal species suggest that this may be a conserved, basic organizational principle of thalamocortical networks. Fragmentary observations in primate sensory nuclei suggest that M-type and C-type cells might be distinguished by their selective expression of calcium binding-proteins. In adult rats, we tested this proposal in a systematic manner throughout the thalamus. Applying Fast-Blue (FB) to a large swath of the pial surface in the lateral aspect of the cerebral hemisphere we labeled a large part of the M-type cell populations in the thalamus and subsequently examined FB co-localization with calbindin or parvalbumin immunoreactivity in thalamic neuron somata. FB-labeled cells were present in large numbers in the ventromedial, interanteromedial, posterior, lateral posterior and medial geniculate nuclei. Distribution of the FB-labeled neuron somata was roughly coextensive with that of the calbindin immunolabeled somata, while parvalbumin immunoreactive somata were virtually absent from dorsal thalamus. Co-localization of FB and calbindin immunolabeling ranged from >95% in the ventromedial and interanteromedial nuclei, to 30% in the dorsal lateral geniculate. Moreover, in the ventromedial and interanteromedial nuclei nearly all of the calbindin-immunoreactive neurons were also labeled with FB. In most other nuclei, however, a major population of M-type cells cannot be identified with calbindin immunolabeling. Consistent with studies in primates and carnivores, present data show that in rats M-type cells are numerous and widely distributed across the rat thalamus; however, calbindin is expressed only by a fraction, albeit a large one, of these cells.
丘脑包含两类主要的投射神经元，它们选择性地支配皮质微回路的不同成分：一类是著名的“特异性”或“核心”（C型）细胞，支配皮质第IV层；另一类是“基质”（M型）细胞，支配第I层。对不同哺乳动物物种的观察表明，这可能是丘脑皮质网络保守的基本组织原则。对灵长类动物感觉核的零散观察表明，M型和C型细胞可能通过其钙结合蛋白的选择性表达来区分。在成年大鼠中，我们在整个丘脑中系统地测试了这一假设。将快蓝（FB）应用于大脑半球外侧软脑膜表面的大片区域，我们标记了丘脑中大部分M型细胞群体，随后检查了FB与丘脑神经元胞体中钙结合蛋白或小白蛋白免疫反应性的共定位情况。在腹内侧核、前内侧核、后核、外侧后核和内侧膝状核中大量存在FB标记的细胞。FB标记的神经元胞体分布与钙结合蛋白免疫标记的胞体大致相同，而背侧丘脑几乎没有小白蛋白免疫反应性胞体。FB和钙结合蛋白免疫标记的共定位范围从腹内侧核和前内侧核中的>95%到背外侧膝状核中的30%。此外，在腹内侧核和前内侧核中，几乎所有钙结合蛋白免疫反应性神经元也被FB标记。然而，在大多数其他核中，用钙结合蛋白免疫标记无法识别主要的M型细胞群体。与灵长类动物和食肉动物的研究一致，目前的数据表明，在大鼠中，M型细胞数量众多，广泛分布于大鼠丘脑；然而，这些细胞中只有一部分（尽管是很大一部分）表达钙结合蛋白。
