Prairie voles (Microtus ochrogaster) and Syrian, or golden, hamsters (Mesocricetus auratus) are closely related to mice (Mus musculus) and are commonly used in studies of social behavior including social interaction, social memory, and aggression. Hippocampal area CA2 is known to play a key role in these behaviors in mice and responds to social stimuli in rats, but CA2 has yet to be characterized in hamsters or voles, which are also used in studies of social behaviors. Here, we used immunofluorescence to determine whether CA2 could be molecularly identified in tissue from voles and hamsters. We found that staining for many CA2 markers was similar in these three species, with labeling seen in neurons at the distal end of the mossy fibers . In contrast, although perineuronal nets (PNNs) surround CA2 cells in mice, PNN staining differed across species. In voles, both CA2 and CA3 were labeled, whereas in hamsters, labeling was seen primarily in CA3. These results demonstrate that CA2 can be molecularly distinguished from neighboring CA1 and CA3 areas in voles and hamsters with several antibodies commonly used in mice. However, PNN staining is not useful for identifying CA2 in voles or hamsters, suggestive of differing roles for either PNNs or for the hippocampal subregions in social behavior. These findings reveal commonalities across species in the molecular profile of CA2 and should facilitate future studies of CA2 in these species.

中文翻译：

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仓鼠和田鼠大脑海马CA2区的鉴定

草原田鼠（黄田田鼠）和叙利亚仓鼠或金色仓鼠（金仓鼠）与小鼠密切相关（小家鼠）并常用于社会行为研究，包括社会互动、社会记忆和攻击性。众所周知，海马区 CA2 在小鼠的这些行为中发挥着关键作用，并且对大鼠的社交刺激做出反应，但 CA2 尚未在仓鼠或田鼠中得到表征，而仓鼠或田鼠也用于社交行为的研究。在这里，我们使用免疫荧光来确定是否可以在田鼠和仓鼠的组织中对 CA2 进行分子鉴定。我们发现这三个物种的许多 CA2 标记物的染色相似，在苔藓纤维远端的神经元中看到标记。相比之下，尽管小鼠的 CA2 细胞周围有神经周围网 (PNN)，但 PNN 染色在不同物种之间存在差异。在田鼠中，CA2 和 CA3 均被标记，而在仓鼠中，标记主要出现在 CA3 中。这些结果表明，利用小鼠常用的几种抗体，可以将田鼠和仓鼠的 CA2 区域与邻近的 CA1 和 CA3 区域进行分子区分。然而，PNN 染色对于识别田鼠或仓鼠中的 CA2 没有用，这表明 PNN 或海马亚区在社会行为中发挥着不同的作用。这些发现揭示了不同物种 CA2 分子谱的共性，并应有助于未来对这些物种中 CA2 的研究。