Behavioral Neurogenetics Laboratory, Department of Psychological Sciences, Purdue University, West Lafayette, Indiana, United States.
Am J Physiol Regul Integr Comp Physiol. 2024 Aug 1;327(2):R173-R187. doi: 10.1152/ajpregu.00252.2023. Epub 2024 Jun 11.
Vagal afferents to the gastrointestinal tract are crucial for the regulation of food intake, signaling negative feedback that contributes to satiation and positive feedback that produces appetition and reward. Vagal afferents to the small intestinal mucosa contribute to this regulation by sensing luminal stimuli and reporting this information to the brain. These afferents respond to mechanical, chemical, thermal, pH, and osmolar stimuli, as well as to bacterial products and immunogens. Surprisingly, little is known about how these stimuli are transduced by vagal mucosal afferents or how their transduction is organized among these afferents' terminals. Furthermore, the effects of stimulus concentration ranges or physiological stimuli on vagal activity have not been examined for some of these stimuli. Also, detection of luminal stimuli has rarely been examined in rodents, which are most frequently used for studying small intestinal innervation. Here we review what is known about stimulus detection by vagal mucosal afferents and illustrate the complexity of this detection using nutrients as an exemplar. The accepted model proposes that nutrients bind to taste receptors on enteroendocrine cells (EECs), which excite them, causing the release of hormones that stimulate vagal mucosal afferents. However, evidence reviewed here suggests that although this model accounts for many aspects of vagal signaling about nutrients, it cannot account for all aspects. A major goal of this review is therefore to evaluate what is known about nutrient absorption and detection and, based on this evaluation, identify candidate mucosal cells and structures that could cooperate with EECs and vagal mucosal afferents in stimulus detection.
胃肠道的迷走传入纤维对于调节摄食至关重要，它们通过传递负反馈信号来促进饱腹感，通过传递正反馈信号来产生食欲和奖励。小肠黏膜的迷走传入纤维通过感知腔室刺激并将此信息报告给大脑来参与这种调节。这些传入纤维对机械、化学、热、pH 值和渗透压刺激以及细菌产物和免疫原做出反应。令人惊讶的是，人们对这些刺激如何被迷走黏膜传入纤维转导，以及它们的转导如何在这些传入纤维的末端之间组织，知之甚少。此外，对于一些刺激物，其刺激浓度范围或生理刺激对迷走神经活动的影响尚未进行研究。此外，很少有研究在啮齿动物中检测腔室刺激物，而啮齿动物通常用于研究小肠神经支配。在这里，我们回顾了迷走黏膜传入纤维对刺激物的检测，并用营养物质作为范例来说明这种检测的复杂性。被接受的模型提出，营养物质与肠内分泌细胞 (EECs) 上的味觉受体结合，从而激活它们，导致刺激迷走黏膜传入纤维的激素释放。然而，这里回顾的证据表明，尽管该模型解释了许多关于营养物质的迷走信号的方面，但它并不能解释所有方面。因此，本篇综述的主要目标是评估关于营养物质吸收和检测的已知内容，并在此评估的基础上，确定候选黏膜细胞和结构，这些细胞和结构可能与 EECs 和迷走黏膜传入纤维在刺激检测中合作。
