The presubiculum, a subarea of the parahippocampal region, plays a critical role in spatial navigation and spatial representation. An outstanding aspect of presubicular spatial codes is head-direction selectivity of firing of excitatory neurons, called head-direction cells. Head-direction selectivity emerges before eye opening in rodents and is maintained in adulthood through neurophysiological interactions between excitatory and inhibitory neurons. Although the presubiculum has been physiologically profiled in terms of spatial representation during development, the histological characteristics of the developing presubiculum are poorly understood. We found that the expression of vesicular glutamate transporter 2 (VGluT2) could be used to delimit the superficial layers of the presubiculum, which was identified using an anterograde tracer injected into the anterior thalamic nucleus. Thus, we immunostained slices from mice ranging in age from neonates to adults using an antibody against VGluT2 to evaluate the VGluT2-positive area, which was identified as the superficial layers of the presubiculum, during development. We also immunostained the slices using antibodies against parvalbumin (PV) and somatostatin (SOM) and found that in the presubicular superficial layers, PV-positive neurons progressively increased in number during development, whereas SOM-positive neurons exhibited no increasing trend. In addition, we observed repeating patch structures in presubicular layer III from postnatal day 12. The abundant expression of VGluT2 suggests that the presubicular superficial layers are regulated primarily by VGluT2-mediated excitatory neurotransmission. Moreover, developmental changes in the densities of PV- and SOM-positive interneurons and the emergence of the VGluT2-positive patch structures during adolescence may be associated with the functional development of spatial codes in the superficial layers of the presubiculum.

中文翻译：

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发育过程中前唇表层的分子表征

前丘脑，海马旁区域的一个子区域，在空间导航和空间表示中起着至关重要的作用。子前空间码的一个突出方面是激发神经元放电的头向选择性，称为头向细胞。头方向选择性在啮齿类动物睁眼之前出现，并通过兴奋性和抑制性神经元之间的神经生理学相互作用维持在成年期。尽管在发育过程中就空间分布而言已对前臼进行了生理学分析，但对发展中的前臼的组织学特征了解甚少。我们发现水泡谷氨酸转运蛋白2（VGluT2）的表达可用于界定前唇浅表层，使用注入丘脑前核的顺行示踪剂进行鉴定。因此，我们使用抗VGluT2的抗体对从新生到成年年龄的小鼠的切片进行了免疫染色，以评估在发育过程中被鉴定为前房浅表层的VGluT2阳性区域。我们还使用针对小白蛋白（PV）和生长抑素（SOM）的抗体对切片进行了免疫染色，发现在亚皮层前浅层中，PV阳性神经元在发育过程中数量逐渐增加，而SOM阳性神经元则没有增加趋势。此外，我们观察到从出生后第12天开始，在亚次皮层的第III层中重复出现了斑块结构。VGluT2的大量表达表明，亚皮层表浅层主要受VGluT2介导的兴奋性神经传递的调节。此外，青春期期间PV和SOM阳性中间神经元密度的发展变化以及VGluT2阳性斑块结构的出现可能与前房浅表层空间代码的功能发展有关。