Laboratoire Matière et Systèmes Complexes UMR 7057, Université Paris Cité/CNRS, Paris, France.
College of Medicine and Public Health, Flinders University, Adelaide, South Australia, Australia.
Exp Physiol. 2024 Sep;109(9):1545-1556. doi: 10.1113/EP091977. Epub 2024 Jul 9.
Gut motility undergoes a switch from myogenic to neurogenic control in late embryonic development. Here, we report on the electrical events that underlie this transition in the enteric nervous system, using the GCaMP6f reporter in neural crest cell derivatives. We found that spontaneous calcium activity is tetrodotoxin (TTX) resistant at stage E11.5, but not at E18.5. Motility at E18.5 was characterized by periodic, alternating high- and low-frequency contractions of the circular smooth muscle; this frequency modulation was inhibited by TTX. Calcium imaging at the neurogenic-motility stages E18.5-P3 showed that Ca1.2-positive neurons exhibited spontaneous calcium activity, which was inhibited by nicardipine and 2-aminoethoxydiphenyl borate (2-APB). Our protocol locally prevented muscle tone relaxation, arguing for a direct effect of nicardipine on enteric neurons, rather than indirectly by its relaxing effect on muscle. We demonstrated that the ENS was mechanosensitive from early stages on (E14.5) and that this behaviour was TTX and 2-APB resistant. We extended our results on L-type channel-dependent spontaneous activity and TTX-resistant mechanosensitivity to the adult colon. Our results shed light on the critical transition from myogenic to neurogenic motility in the developing gut, as well as on the intriguing pathways mediating electro-mechanical sensitivity in the enteric nervous system. HIGHLIGHTS: What is the central question of this study? What are the first neural electric events underlying the transition from myogenic to neurogenic motility in the developing gut, what channels do they depend on, and does the enteric nervous system already exhibit mechanosensitivity? What is the main finding and its importance? ENS calcium activity is sensitive to tetrodotoxin at stage E18.5 but not E11.5. Spontaneous electric activity at fetal and adult stages is crucially dependent on L-type calcium channels and IPR receptors, and the enteric nervous system exhibits a tetrodotoxin-resistant mechanosensitive response. Abstract figure legend Tetrodotoxin-resistant Ca rise induced by mechanical stimulation in the E18.5 mouse duodenum.
肠道运动在胚胎后期发育中从肌源性向神经源性控制发生转变。在这里，我们使用神经嵴细胞衍生物中的 GCaMP6f 报告基因，报告了在肠神经系统中发生这种转变的电事件。我们发现自发钙活性在 E11.5 时对河豚毒素（TTX）具有抗性，但在 E18.5 时没有。E18.5 的运动表现为周期性的、交替的高、低频环行平滑肌收缩；这种频率调制被 TTX 抑制。在神经源性-运动阶段 E18.5-P3 进行钙成像显示，Ca1.2 阳性神经元表现出自发钙活性，该活性被尼卡地平（nicardipine）和 2-氨基乙基二磷酸（2-APB）抑制。我们的方案局部阻止了肌肉张力的松弛，这表明尼卡地平对肠神经元具有直接作用，而不是通过其对肌肉的松弛作用间接作用。我们证明，从早期（E14.5）开始肠神经系统就具有机械敏感性，并且这种行为对 TTX 和 2-APB 具有抗性。我们将我们关于 L 型通道依赖性自发活性和 TTX 抗性机械敏感性的结果扩展到成年结肠。我们的结果揭示了从发育中的肠道的肌源性向神经源性运动的关键转变，以及介导肠神经系统的电-机械敏感性的有趣途径。重点：这项研究的核心问题是什么？在发育中的肠道中，从肌源性向神经源性运动转变的第一个神经电事件是什么，它们依赖于哪些通道，以及肠神经系统是否已经表现出机械敏感性？主要发现及其重要性是什么？在 E18.5 阶段，肠神经系统的钙活性对 TTX 敏感，但在 E11.5 阶段不敏感。胎儿和成年阶段的自发电活动主要依赖于 L 型钙通道和 IPR 受体，并且肠神经系统表现出 TTX 抗性的机械敏感反应。
