Appetite or feeding motivation relies significantly on food odors. In the blowfly Phormia regina, feeding motivation for sucrose is decreased by the odor of d-limonene but increased by the odor of 1-octen-3-ol odor. These flies have antennal lobes (ALs) consisting of several tens of glomerular pairs as a primary olfactory center in the brain. Odor information from different olfactory organs—specifically, the antennae and maxillary palps—goes to the corresponding glomeruli. To investigate how odors differently affect feeding motivation, we identified the olfactory organs and glomeruli that are activated by nonappetitive and appetitive odors. We first constructed a glomerular map of the antennal lobe in P. regina. Anterograde fluorescence labeling of antennal and maxillary afferent nerves, both of which project into the contralateral and ipsilateral ALs, revealed differential staining in glomerular regions. Some of the axonal fiber bundles from the antennae and maxillary palps projected to the subesophageal ganglion (SOG). We visualized the activation of the glomeruli in response to odor stimuli by immunostaining phosphorylated extracellular signal-regulated kinase (pERK). We observed different glomerulus activation under different odor stimulations. Referring to our glomerular map, we determined that antennal exposure to d-limonene odor activated the DA13 glomeruli, while exposure of the maxillary palps to 1-octen-3-ol activated the MxB1 glomeruli. Our results indicated that a nonappetitive odor input from the antennae and an appetitive odor input from the maxillary palps activate different glomeruli in the different regions of ALs in the blowfly P. regina. Collectively, our findings suggest that compartmentalization of glomeruli in AL is essential for proper transmission of odor information.

中文翻译：

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苍蝇 Phormia regina 中两种嗅觉器官通过非食欲性 D-柠檬烯和食欲性 1-辛烯-3-醇气味激活的触角叶肾小球的可视化

食欲或进食动机很大程度上取决于食物的气味。在绿头蝇Phormia regina中，d-柠檬烯的气味降低了对蔗糖的摄食动机，但1-辛烯-3-醇的气味增加了蔗糖的摄食动机。这些果蝇的触角叶 (AL) 由数十对肾小球组成，作为大脑中的主要嗅觉中心。来自不同嗅觉器官（特别是触角和上颌须）的气味信息会传送到相应的肾小球。为了研究气味如何不同地影响进食动机，我们确定了被非食欲和食欲气味激活的嗅觉器官和肾小球。我们首先构建了 P. regina 触角叶的肾小球图。触角和上颌传入神经均投射到对侧和同侧 AL 中，顺行荧光标记显示肾小球区域的差异染色。一些来自触角和上颌须的轴突纤维束投射到食管下神经节（SOG）。我们通过对磷酸化细胞外信号调节激酶（pERK）进行免疫染色，观察了肾小球响应气味刺激的激活情况。我们观察到不同气味刺激下不同的肾小球激活。参考我们的肾小球图，我们确定触角暴露于 d-柠檬烯气味会激活 DA13 肾小球，而上颌须暴露于 1-octen-3-ol 会激活 MxB1 肾小球。我们的结果表明，来自触角的非食欲性气味输入和来自上颌须的食欲性气味输入激活了绿头蝇 AL 不同区域的不同肾小球。总的来说，我们的研究结果表明 AL 中肾小球的区室化对于气味信息的正确传递至关重要。