Abstract：
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 CaV1.2-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 IP3R receptors, and the enteric nervous system exhibits a tetrodotoxin-resistant mechanosensitive response. Abstract figure legend Tetrodotoxin-resistant Ca2+ rise induced by mechanical stimulation in the E18.5 mouse duodenum.
摘要：
在胚胎发育后期，肠道运动经历了从肌源性控制到神经源性控制的转变。这里,我们报道了肠神经系统这种转变背后的电事件，在神经c细胞衍生物中使用GCaMP6f报告基因。我们发现自发钙活性在阶段E11.5具有抗河豚毒素（TTX），但在E18.5没有。E18.5的运动性具有周期性，环形平滑肌的高频和低频交替收缩；这种频率调制被TTX抑制。神经源性运动阶段的钙成像E18.5-P3显示CaV1.2阳性神经元表现出自发的钙活性，尼卡地平和2-氨基乙氧基二苯基硼酸酯（2-APB）抑制了。我们的方案局部阻止了肌肉紧张放松，争论尼卡地平对肠神经元的直接作用，而不是间接地通过它对肌肉的放松作用。我们证明了ENS从早期阶段就对机械敏感（E14.5），并且这种行为对TTX和2-APB具有抗性。我们扩展了对成年结肠的L型通道依赖性自发活动和TTX抗性机械敏感性的结果。我们的结果揭示了在发育中的肠道中从肌源性运动到神经源性运动的关键转变，以及介导肠神经系统机电敏感性的有趣途径。重点：这项研究的中心问题是什么？在发育中的肠道中，从肌源性运动到神经源性运动转变的第一个神经电事件是什么？他们依赖什么渠道，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？ENS钙活性在E18.5阶段对河豚毒素敏感，但在E11.5阶段不敏感。胎儿和成人阶段的自发电活动主要取决于L型钙通道和IP3R受体，肠神经系统表现出抗河豚毒素的机械敏感反应。附图说明机械刺激诱导E18.5小鼠十二指肠抗河豚毒素Ca2+升高。
