Modern research on gastrointestinal behavior has revealed it to be a highly complex bidirectional process in which the gut sends signals to the brain, via spinal and vagal visceral afferent pathways, and receives sympathetic and parasympathetic inputs. Concomitantly, the enteric nervous system within the bowel, which contains intrinsic primary afferent neurons, interneurons, and motor neurons, also senses the enteric environment and controls the detailed patterns of intestinal motility and secretion. The vast microbiome that is resident within the enteric lumen is yet another contributor, not only to gut behavior, but to the bidirectional signaling process, so that the existence of a microbiota-gut-brain “connectome” has become apparent. The interaction between the microbiota, the bowel, and the brain now appears to be neither a top-down nor a bottom-up process. Instead, it is an ongoing, tripartite conversation, the outline of which is beginning to emerge and is the subject of this Review. We emphasize aspects of the exponentially increasing knowledge of the microbiota-gut-brain “connectome” and focus attention on the roles that serotonin, Toll-like receptors, and macrophages play in signaling as exemplars of potentially generalizable mechanisms.

对胃肠行为的现代研究表明，这是一个高度复杂的双向过程，肠道通过脊髓和迷走神经内脏传入通路向大脑发送信号，并接收交感神经和副交感神经的输入。与此同时，肠道内的肠神经系统包含固有的初级传入神经元、中间神经元和运动神经元，也感知肠道环境并控制肠道运动和分泌的详细模式。肠腔内存在的大量微生物群是另一个贡献者，不仅对肠道行为，而且对双向信号传导过程也有贡献，因此微生物群-肠-脑“连接组”的存在已经变得显而易见。微生物群、肠道和大脑之间的相互作用现在看来既不是自上而下也不是自下而上的过程。相反，这是一场持续的三方对话，其轮廓正在开始显现，也是本次审查的主题。我们强调对微生物群-肠-脑“连接组”的知识呈指数增长的各个方面，并将注意力集中在血清素、Toll 样受体和巨噬细胞在信号传导中所发挥的作用，作为潜在普遍机制的范例。