Institut de Génomique Fonctionnelle, Montpellier, France; Inserm U661, Montpellier, France.
Hippocampus. 2012 Dec;22(12):2199-207. doi: 10.1002/hipo.22044. Epub 2012 Jul 6.
The hippocampal formation is part of an anatomical system critically involved in learning and memory. Increasing evidence suggests that dopamine plays an important role in learning and memory as well as in several forms of synaptic plasticity. However, the precise identification of neuronal populations expressing D1 or D2 dopamine receptors within the hippocampus is still lacking. To clarify this issue, we used BAC transgenic mice expressing enhanced green fluorescent protein (EGFP) under the control of the promoter of dopamine D1 or D2 receptors. In Drd1a-EGFP mice, sparse GFP-expressing neurons were detected among glutamatergic projecting neurons of the granular layer of the dentate gyrus and GABAergic interneurons located in the hilus. A dense immunofluorescence was observed in the outer and medial part of the molecular layer of the dentate gyrus as well as in the inner part of the molecular layer of CA1 corresponding to the terminals of pyramidal neurons of the entorhinal cortex defining the perforant and the temporo-ammonic pathway respectively. Finally, scattered D1 receptor-expressing neurons were also identified as GABAergic interneurons in the CA3/CA1 fields of the hippocampus. In Drd2-EGFP transgenic mice, GFP was exclusively detected in the glutamatergic mossy cells located in the polymorphic layer of the dentate gyrus. This pattern was confirmed in Drd2-Cre mice crossed with NLS-LacZ-Tau(mGFP) :LoxP and RCE:LoxP reporter lines. Our results demonstrate that D1 and D2 receptor-expressing neurons are strictly segregated in the mouse hippocampus. By clarifying the identity of D1 and D2 receptor-expressing neurons in the hippocampus, this study establishes a basis for future investigations aiming at elucidating their roles in the hippocampal network.
海马结构是参与学习和记忆的解剖系统的一部分。越来越多的证据表明，多巴胺在学习和记忆以及几种形式的突触可塑性中都起着重要作用。然而，海马内表达 D1 或 D2 多巴胺受体的神经元群体的确切鉴定仍然缺乏。为了解决这个问题，我们使用了 BAC 转基因小鼠，这些小鼠在多巴胺 D1 或 D2 受体启动子的控制下表达增强型绿色荧光蛋白（EGFP）。在 Drd1a-EGFP 小鼠中，稀疏的 GFP 表达神经元在齿状回颗粒层的谷氨酸能投射神经元和位于门区的 GABA 能中间神经元中被检测到。在外层和分子层的内侧部分以及 CA1 的分子层的内层观察到密集的免疫荧光，这些部位对应于来自内嗅皮层的锥体细胞的末端，分别定义了穿通和颞颌下途径。最后，在海马 CA3/CA1 区也鉴定出散在的 D1 受体表达神经元作为 GABA 能中间神经元。在 Drd2-EGFP 转基因小鼠中，GFP 仅在位于齿状回多形层的谷氨酸能苔藓细胞中被检测到。这种模式在与 NLS-LacZ-Tau(mGFP) :LoxP 和 RCE:LoxP 报告线杂交的 Drd2-Cre 小鼠中得到了证实。我们的结果表明，D1 和 D2 受体表达神经元在小鼠海马中严格分离。通过阐明海马内 D1 和 D2 受体表达神经元的特性，本研究为未来旨在阐明其在海马网络中的作用的研究奠定了基础。
