Mushroom body output neurons MBONa1/a2 define an odor intensity channel that regulates behavioral odor discrimination learning in larval Drosophila
Mushroom body output neurons MBONa1/a2 define an odor intensity channel that regulates behavioral odor discrimination learning in larval Drosophila
复制标题
蘑菇体输出神经元 MBONa1/a2 定义了一个气味强度通道，调节果蝇幼虫的行为气味辨别学习
DOI：
10.1101/2022.12.14.518530
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Mohamed A
中科院分区：
文献类型：
--
作者：
Mohamed A
动物对感觉输入的敏感性必须加以调节，以确保信号被检测到并可被辨别。然而，电路如何调节对感官刺激的敏感性的动态范围还没有很好的理解。一个给定的气味表示在昆虫蘑菇体（MB）的稀疏组合编码的凯尼恩细胞（KC），形成一个气味质量表示。为了解决如何在MB输入区域，花萼的水平上处理感官刺激的强度，我们的特点是一组新的蘑菇体输出神经元，优先响应高气味浓度。我们发现，一对MB萼输出神经元，MBON-A1/2，是突触后的MB萼，在那里他们收到广泛的突触输入KC树突，抑制反馈神经元APL，和章鱼胺能sVUM 1神经元，但相对较少的输入投射神经元。这种模式在第三龄幼虫以及第一龄连接体中大致一致。MBON-a1/a2突触前终末直接支配同侧和对侧大脑半球中MB内侧叶输出区域周围的区域。通过使用jRCamP 1b监测钙活性，我们发现MBON-a1/a2反应是气味浓度依赖性的，仅对高于200倍稀释度的乙酸乙酯（EA）浓度作出反应，而MB神经元的浓度更稳定，对EA稀释度低至10-4作出反应。起源于SEZ（食管下区）的花萼支配的sVUM 1调节神经元的光遗传激活对MBON-a1/a2气味反应没有显示出可检测的影响。与对照组相比，使用CsChrimson的MBON-a1/a2的光遗传激活损害了气味辨别学习。我们建议，MBON-a1/a2形成的输出通道的花萼，汇总收敛的感觉和调制输入，发射优先高气味浓度，并可能影响下游MB目标的活动。
The sensitivity of animals to sensory input must be regulated to ensure that signals are detected and also discriminable. However, how circuits regulate the dynamic range of sensitivity to sensory stimuli is not well understood. A given odor is represented in the insect mushroom bodies (MBs) by sparse combinatorial coding by Kenyon cells (KCs), forming an odor quality representation. To address how intensity of sensory stimuli is processed at the level of the MB input region, the calyx, we characterized a set of novel mushroom body output neurons that respond preferentially to high odor concentrations. We show that a pair of MB calyx output neurons, MBON-a1/2, are postsynaptic in the MB calyx, where they receive extensive synaptic inputs from KC dendrites, the inhibitory feedback neuron APL, and octopaminergic sVUM1 neurons, but relatively few inputs from projection neurons. This pattern is broadly consistent in the third-instar larva as well as in the first instar connectome. MBON-a1/a2 presynaptic terminals innervate a region immediately surrounding the MB medial lobe output region in the ipsilateral and contralateral brain hemispheres. By monitoring calcium activity using jRCamP1b, we find that MBON-a1/a2 responses are odor-concentration dependent, responding only to ethyl acetate (EA) concentrations higher than a 200-fold dilution, in contrast to MB neurons which are more concentration-invariant and respond to EA dilutions as low as 10–4. Optogenetic activation of the calyx-innervating sVUM1 modulatory neurons originating in the SEZ (Subesophageal zone), did not show a detectable effect on MBON-a1/a2 odor responses. Optogenetic activation of MBON-a1/a2 using CsChrimson impaired odor discrimination learning compared to controls. We propose that MBON-a1/a2 form an output channel of the calyx, summing convergent sensory and modulatory input, firing preferentially to high odor concentration, and might affect the activity of downstream MB targets.