Molecular Medicine Program, University of Utah, Salt Lake City, UT, USA.
Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.
BMC Biol. 2021 Feb 16;19(1):31. doi: 10.1186/s12915-021-00969-7.
Proper regulation of feeding is important for an organism's well-being and survival and involves a motivational component directing the search for food. Dissecting the molecular and neural mechanisms of motivated feeding behavior requires assays that allow quantification of both motivation and food intake. Measurements of motivated behavior usually involve assessing physical effort or overcoming an aversive stimulus. Food intake in Drosophila can be determined in a number of ways, including by measuring the time a fly's proboscis interacts with a food source associated with an electrical current in the fly liquid-food interaction counter (FLIC). Here, we show that electrical current flowing through flies during this interaction is aversive, and we describe a modified assay to measure motivation in Drosophila.
Food intake is reduced during the interaction with FLIC when the electrical current is turned on, which provides a confounding variable in studies of motivated behavior. Based on the FLIC, we engineer a novel assay, the fly liquid-food electroshock assay (FLEA), which allows for current adjustments for each feeding well. Using the FLEA, we show that both external incentives and internal motivational state can serve as drivers for flies to overcome higher current (electric shock) to obtain superior food. Unlike similar assays in which bitterness is the aversive stimulus for the fly to overcome, we show that current perception is not discounted as flies become more food-deprived. Finally, we use genetically manipulated flies to show that neuropeptide F, an orthologue of mammalian NPY previously implicated in regulation of feeding motivation, is required for sensory processing of electrical current.
The FLEA is therefore a novel assay to accurately measure incentive motivation in Drosophila. Using the FLEA, we also show that neuropeptide F is required for proper perception or processing of an electroshock, a novel function for this neuropeptide involved in the processing of external and internal stimuli.
适当的进食调节对于生物体的健康和生存至关重要，其中涉及到一个引导寻找食物的动机成分。解析动机性摄食行为的分子和神经机制需要能够定量测量动机和食物摄入的检测方法。动机行为的测量通常涉及评估身体努力或克服厌恶刺激。在果蝇中，可以通过多种方式确定食物摄入，包括测量果蝇的喙与与电流相关的食物源相互作用的时间，该电流在果蝇液体食物相互作用计数器（FLIC）中。在这里，我们表明，在与 FLIC 相互作用期间，流过果蝇的电流是厌恶的，我们描述了一种改良的测定方法来测量果蝇的动机。
当电流开启时，与 FLIC 的相互作用会减少食物摄入，这在动机行为的研究中是一个混杂变量。基于 FLIC，我们设计了一种新颖的测定方法，即果蝇液体食物电休克测定（FLEA），它允许为每个喂食井调整电流。使用 FLEA，我们表明，外部激励和内部动机状态都可以作为驱动因素，使果蝇克服更高的电流（电击）以获得更好的食物。与类似的实验不同，苦味是果蝇克服的厌恶刺激，我们表明，随着果蝇变得更加饥饿，电流感知不会被折扣。最后，我们使用基因改造的果蝇表明，神经肽 F 是一种与哺乳动物 NPY 同源的肽，先前被认为与进食动机的调节有关，是果蝇对电流进行感觉处理所必需的。
因此，FLEA 是一种新颖的测定方法，可以准确测量果蝇的激励动机。使用 FLEA，我们还表明，神经肽 F 是正确感知或处理电击所必需的，这是一种涉及外部和内部刺激处理的新型神经肽功能。
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