Aversive cues fail to activate fos expression in the asymmetric olfactory-habenula pathway of zebrafish
Aversive cues fail to activate fos expression in the asymmetric olfactory-habenula pathway of zebrafish
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DOI：
10.3389/fncir.2013.00098
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发表时间：
2013-05-21
影响因子：
3.5
通讯作者：
Halpern, Marnie E.
中科院分区：
文献类型：
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作者：
deCarvalho, Tagide N.;Akitake, Courtney M.;Halpern, Marnie E.
斑马鱼上皮层的缰核背侧核已成为研究脊椎动物大脑左右不对称(L-R)的发展及其功能的有价值的模型。两侧成对的背缰核在大小、神经解剖组织和分子特性上表现出显著的差异。它们在与脚间核(IPN)的传出联系和它们的传入输入上也表现出不同，分布在嗅球两侧的二尖瓣细胞亚群只支配右侧缰核。以前的研究表明，背缰核参与调节幼年和成年斑马鱼的恐惧/焦虑反应。选择性标记lhx2a：yfp转基因后发现的不对称嗅觉-缰核通路(OB-Ha)介导了报警信息素引起的恐惧行为。在这里，我们表明，Fam84b基因的表达划定了右侧缰核的一个独特区域，这是lhx2a：yfp标记的嗅轴突的神经支配部位。当切除副松果体时，通常促进左侧缰核的同一性；在背缰核和1hx2a中都存在Fam84b区域：YFP标记的嗅球神经元在左侧和右侧形成突触。为了探索不对称嗅觉投射的相关性以及它可能如何影响缰核功能，我们使用已知的唤起行为的气味物质来测试这一途径的激活。我们发现，警报物质或其他令人厌恶的气味，以及吸引人的线索，可以激活嗅球细胞亚群中FOS的表达，但不能激活表达lhx2a：YFP的群体。此外，报警信息素和硫酸软骨素都不能引起缰核背侧FOS的激活。结果表明，上皮神经元的L-R不对称性决定了嗅觉神经支配的方向性，而Lhx2a：YFP OB-Ha通路似乎并不介导对厌恶气味的恐惧反应。
The dorsal habenular nuclei of the zebrafish epithalamus have become a valuable model for studying the development of left-right (L-R) asymmetry and its function in the vertebrate brain. The bilaterally paired dorsal habenulae exhibit striking differences in size, neuroanatomical organization, and molecular properties. They also display differences in their efferent connections with the interpeduncular nucleus (IPN) and in their afferent input, with a subset of mitral cells distributed on both sides of the olfactory bulb innervating only the right habenula. Previous studies have implicated the dorsal habenulae in modulating fear/anxiety responses in juvenile and adult zebrafish. It has been suggested that the asymmetric olfactory-habenula pathway (OB-Ha), revealed by selective labeling from an lhx2a:YFP transgene, mediates fear behaviors elicited by alarm pheromone. Here we show that expression of the fam84b gene demarcates a unique region of the right habenula that is the site of innervation by lhx2a:YFP-labeled olfactory axons. Upon ablation of the parapineal, which normally promotes left habenular identity; the fam84b domain is present in both dorsal habenulae and lhx2a:YFP-labeled olfactory bulb neurons form synapses on the left and the right side. To explore the relevance of the asymmetric olfactory projection and how it might influence habenular function, we tested activation of this pathway using odorants known to evoke behaviors. We find that alarm substance or other aversive odors, and attractive cues, activate fos expression in subsets of cells in the olfactory bulb but not in the lhx2a:YFP expressing population. Moreover, neither alarm pheromone nor chondroitin sulfate elicited fos activation in the dorsal habenulae. The results indicate that L-R asymmetry of the epithalamus sets the directionality of olfactory innervation, however, the lhx2a:YFP OB-Ha pathway does not appear to mediate fear responses to aversive odorants.