大脑皮层的前板包含连接皮层原基与皮层下的投射神经元。这些统称为先锋神经元。在预板隔板之后,这些先驱神经元大部分变成了亚板神经元.某些前板神经元,然而,从不与子板块相关联,而是与边缘区域相关联。在本概述中,我们提出了将啮齿动物中的非亚板先驱神经元分为两种亚型的新分类。在老鼠身上,第一个亚型的神经元是钙结合蛋白(+)(CB),calretinin(CR)和L1()位于隔板之前的预板上部。第二个亚型的神经元是TAG-1(),并且位于前板中先前种群的较深位置。在预板隔板之后,CB(+),CR()和L1()神经元保留在边缘区,而TAG-1()神经元暂时位于上皮质板中。在老鼠身上,相比之下,钙结合蛋白没有标记先驱神经元.我们在小鼠中定义了非亚板先驱神经元的两种亚型,L1(+)或TAG-1(+)/cntn2(+)。我们认为这些是大鼠非亚板先驱神经元的两种亚型的同源物。这些神经元群体的解剖分布在大鼠和小鼠中是相似的。两个非亚板先驱神经元的轴突投影不同。L1()先驱神经元的轴突投射到神经节隆起和前视区域,但是避免进入内囊的后肢朝向丘脑。TAG-1()先驱神经元的轴突在皮质组织发生的早期阶段投射到神经节隆起的外侧部分。
The preplate of the cerebral cortex contains projection neurons that connect the cortical primordium with the subpallium. These are collectively named pioneer neurons. After preplate partition, most of these pioneer neurons become subplate neurons. Certain preplate neurons, however, never associate with the subplate but rather with the marginal zone. In the present overview, we propose a novel classification of non-subplate pioneer neurons in rodents into two subtypes. In rats, the neurons of the first subtype are calbindin(+) (CB), calretinin(+) (CR) and L1(+) and are situated in the upper part of the preplate before its partition. Neurons of the second subtype are TAG-1(+) and are located slightly deeper to the previous population in the preplate. After the preplate partition, the CB(+), CR(+) and L1(+) neurons remain in the marginal zone whereas TAG-1(+) neurons become transiently localized in the upper cortical plate. In mice, by contrast, calcium binding proteins did not label pioneer neurons. We define in mice two subtypes of non-subplate pioneer neurons, either L1(+) or TAG-1(+)/cntn2(+). We propose these to be the homologues of the two subtypes of non-subplate pioneer neurons of rats. The anatomical distribution of these neuron populations is similar in rats and mice. The two populations of non-subplate pioneer neurons differ in their axonal projections. Axons of L1(+) pioneer neurons project to the ganglionic eminences and the anterior preoptic area, but avoid entering the posterior limb of the internal capsule towards the thalamus. Axons of TAG-1(+) pioneer neurons project to the lateral parts of the ganglionic eminences at the early stages of cortical histogenesis examined.