Untypical connectivity from olfactory sensory neurons expressing OR37 into higher brain centers visualized by genetic tracing
Untypical connectivity from olfactory sensory neurons expressing OR37 into higher brain centers visualized by genetic tracing
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DOI：
10.1007/s00418-012-0919-2
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发表时间：
2012-05-01
影响因子：
2.3
通讯作者：
Strotmann, Joerg
中科院分区：
文献类型：
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作者：
Bader, Andrea;Breer, Heinz;Strotmann, Joerg
气味受体（ORs）的OR 37亚家族仅存在于哺乳动物中。与一般的OR相反，它们在物种内和物种间高度保守。这些独特的特征提出了一个问题，即OR 37感觉细胞收集的嗅觉信息是否在特别指定的大脑区域进行处理。为了阐明从OR 37肾小球投射神经元到高级脑区的布线，进行了示踪实验。DiI到腹侧区的嗅球，其中窝藏OR 37肾小球的应用程序，导致标记的纤维不仅在典型的嗅觉皮层区域，但也在内侧杏仁核和下丘脑。为了更精确地可视化来自定义的OR 37肾小球的投射，研究了嗅觉感觉神经元共表达受体亚型OR 37 C和跨突触示踪剂麦胚凝集素（WGA）的转基因小鼠。WGA不仅在OR 37 C感觉神经元和相应的OR 37 C肾小球中可见，而且在位于邻近OR 37 C肾小球的二尖瓣/簇状细胞层中的细胞胞体中可见，表明WGA转移到投射神经元上。在大脑中，WGA免疫反应性在典型的嗅觉皮质区检测不到，而是在内侧杏仁核的不同区域。详细的映射显示，WGA免疫反应仅限于内侧杏仁核的后背亚核。此外，在下丘脑的一些界限分明的区域中可见WGA免疫反应性。这些结果表明从OR 37 C感觉细胞到高级脑中心的独特连接。
The OR37 subfamily of odorant receptors (ORs) exists exclusively in mammals. In contrast to ORs in general, they are highly conserved within and across species. These unique features raise the question, whether olfactory information gathered by the OR37 sensory cells is processed in specially designated brain areas. To elucidate the wiring of projection neurons from OR37 glomeruli into higher brain areas, tracing experiments were performed. The application of DiI onto the ventral area of the olfactory bulb, which harbors the OR37 glomeruli, led to the labeling of fibers not only in the typical olfactory cortical regions, but also in the medial amygdala and the hypothalamus. To visualize the projections from a defined OR37 glomerulus more precisely, transgenic mice were studied in which olfactory sensory neurons co-express the receptor subtype OR37C and the transsynaptic tracer wheat germ agglutinin (WGA). WGA became visible not only in the OR37C sensory neurons and the corresponding OR37C glomerulus, but also in cell somata located in the mitral/tufted cell layer adjacent to the OR37C glomerulus, indicating a transfer of WGA onto projection neurons. In the brain, WGA immunoreactivity was not detectable in typical olfactory cortical areas, but instead in distinct areas of the medial amygdala. Detailed mapping revealed that the WGA immunoreactivity was restricted to the posterior-dorsal subnucleus of the medial amygdala. In addition, WGA immunoreactivity was visible in some well-circumscribed areas of the hypothalamus. These results are indicative for a unique connectivity from OR37C sensory cells into higher brain centers.