Identification of motor neurons and a mechanosensitive sensory neuron in the defecation circuitry of Drosophila larvae.
Identification of motor neurons and a mechanosensitive sensory neuron in the defecation circuitry of Drosophila larvae.
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作者：
Zhang W;Yan Z;Li B;Jan LY;Jan YN
排便可以让身体排除废物，这是动物生存食品加工中的一个重要步骤。与对进食的广泛研究相反，直到最近，它的必然对应物——排便——才受到较少的关注。在这项研究中，我们报告了果蝇幼虫排便行为的特征及其神经基础。果蝇幼虫表现出固定频率的排便周期，涉及后肠和肛门括约肌的顺序收缩。排便行为需要两组运动神经元，分别支配后肠和肛门括约肌，并能直接兴奋肠道肌肉。体内 Ca2+ 成像显示，这两组运动神经元以与排便行为相同的周期依次放电。此外，我们还发现了一个单一的机械敏感感觉神经元，它支配肛缝并感知肠末端的开口。该肛门感觉神经元依赖 TRP 通道 NOMPC，但不依赖 INACTIVE、NANCHUNG 或 PIEZO 进行机械转导。 DOI：http://dx.doi.org/10.7554/eLife.03293.001 在动物中，食物消化的最后阶段是清除体内废物。然而，直到最近，与消化的其他方面（例如进食行为和营养）相比，排便受到的关注还较少。果蝇，也称为果蝇，在研究中通常用作动物生物学模型。当肠壁周围的肌肉收缩时，食物就会通过果蝇幼虫的消化道。这个过程一直持续到废物到达肛门并被排出体外。现在张等人。研究发现，当果蝇幼虫排便时，肠道末端的肌肉会先于肛门的肌肉收缩。神经系统通过分别连接到肠道和肛门肌肉的两组神经细胞的顺序发射来控制这些肌肉。张等人。还发现了一种神经细胞，可以感知肛门何时打开，并将此信息传递回神经系统。当肛门开口拉伸时，神经细胞会被激活，这一过程需要一种称为 NOMPC 的蛋白质。排便问题会导致便秘和其他疾病。例如，先天性巨结肠症（一种影响四千分之一的人的出生缺陷）是由控制肠道肌肉的神经细胞发育异常引起的。果蝇实验可以帮助我们了解人类排便的原理，并开发新的疾病治疗方法。 DOI：http://dx.doi.org/10.7554/eLife.03293.002
Defecation allows the body to eliminate waste, an essential step in food processing for animal survival. In contrast to the extensive studies of feeding, its obligate counterpart, defecation, has received much less attention until recently. In this study, we report our characterizations of the defecation behavior of Drosophila larvae and its neural basis. Drosophila larvae display defecation cycles of stereotypic frequency, involving sequential contraction of hindgut and anal sphincter. The defecation behavior requires two groups of motor neurons that innervate hindgut and anal sphincter, respectively, and can excite gut muscles directly. These two groups of motor neurons fire sequentially with the same periodicity as the defecation behavior, as revealed by in vivo Ca2+ imaging. Moreover, we identified a single mechanosensitive sensory neuron that innervates the anal slit and senses the opening of the intestine terminus. This anus sensory neuron relies on the TRP channel NOMPC but not on INACTIVE, NANCHUNG, or PIEZO for mechanotransduction. DOI: http://dx.doi.org/10.7554/eLife.03293.001 In animals, the final stage in the digestion of food is the removal of waste from the body. Until recently, however, defecation has received less attention than other aspects of digestion such as feeding behavior and nutrition. Fruit flies, also known as Drosophila, are commonly used in research as a model of animal biology. Food is moved through the digestive tract of fruit fly larvae when the muscles that circle the wall of the intestine contract. This process continues until the waste reaches the anus and is expelled from the body. Now Zhang et al. have found that when fruit fly larvae defecate, the muscles at the end of the intestine contract just before the muscles in the anus contract. The nervous system controls these muscles via sequential firing of two sets of nerve cells that connect to the intestine and anus muscles, respectively. Zhang et al. also identified a nerve cell that can sense when the anus is opened and relay this information back to the nervous system. The nerve cell is activated when stretched by the opening of the anus in a process that requires a protein called NOMPC. Problems with defecation can lead to constipation and other diseases. For example, Hirschsprung's disease—a birth defect that affects one in 4000—is caused by abnormal development of the nerve cells that control muscles in the gut. Experiments on fruit flies could help us to understand how defecation works in humans and to develop new treatments for disease. DOI: http://dx.doi.org/10.7554/eLife.03293.002