Koh Sang Don, Lee Ji Yeon, Ryoo Seung-Bum, Drumm Bernard T, Kim Hyun Jin, Baker Sal A, Sanders Kenton M
Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA.
Department of Surgery, Seoul National University Hospital, Seoul National University, Seoul, South Korea.
J Physiol. 2024 Dec;602(24):6659-6682. doi: 10.1113/JP287315. Epub 2024 Nov 21.
The peristaltic reflex has been a central concept in gastrointestinal motility; however, evidence was published recently suggesting that post-stimulus responses that follow inhibitory neural responses provide the main propulsive force in colonic motility. This new concept was based on experiments on proximal colon where enteric inhibitory neural inputs are mainly nitrergic. However, the nature of inhibitory neural inputs changes from proximal to distal colon where purinergic inhibitory regulation dominates. In spite of the transition from nitrergic to purinergic regulation, post-stimulus responses and propulsive contractions were both blocked by antagonists of a conductance (ANO1) exclusive to interstitial cells of Cajal (ICC). How purinergic neurotransmission, transduced by PDGFRα cells, can influence ANO1 in ICC is unknown. We compared neural responses in proximal and distal colon. Post-stimulus responses were blocked by inhibition of nitrergic neurotransmission in proximal colon, but P2Y1 receptor antagonists were more effective in distal colon. Ca entry through voltage-dependent channels (Ca3) enhances Ca release in ICC. Thus, we reasoned that hyperpolarization caused by purinergic responses in PDGFRα cells, which are electrically coupled to ICC, might decrease inactivation of Ca3 channels and activate Ca entry into ICC via anode-break upon cessation of inhibitory responses. Post-stimulus responses in distal colon were blocked by MRS2500 (P2Y1 receptor antagonist), apamin (SK channel antagonist) and NNC55-0396 (Ca3 antagonist). These compounds also blocked propagating contractions in mid and distal colon. These data provide the first clear demonstration that integration of functions in the smooth muscle-ICC-PDGFRα cell (SIP) syncytium generates a major motility behaviour. KEY POINTS: Propagating propulsive contractions initiated by the enteric nervous system are a major motility behaviour in the colon. A major component of contractions, necessary for propulsive contractions, occurs at cessation of enteric inhibitory neurotransmission (post-stimulus response) and is generated by interstitial cells of Cajal (ICC), which are electrically coupled to smooth muscle cells. The nature of enteric inhibitory neurotransmission shifts from proximal colon, where it is predominantly due to nitric oxide, to distal colon, where it is predominantly due to purine neurotransmitters. Different cells transduce nitric oxide and purines in the colon. ICC transduce nitric oxide, but another type of interstitial cell, PDGFRα cells, transduces input from purinergic neurons. However, the post-stimulus responses in proximal and distal colon are still generated in ICC. This paper explores how integrated behaviours of ICC, PDGFRα cells and smooth muscle cells accomplish propulsive motility in the colon.
蠕动反射一直是胃肠运动的核心概念;然而,最近发表的证据表明,抑制性神经反应后的刺激后反应是结肠运动的主要推进力。这一新概念基于对近端结肠的实验,近端结肠中肠内抑制性神经输入主要是一氧化氮能的。然而,抑制性神经输入的性质从近端结肠到远端结肠发生变化,在远端结肠中嘌呤能抑制调节占主导。尽管从一氧化氮能调节转变为嘌呤能调节,但刺激后反应和推进性收缩均被Cajal间质细胞(ICC)特有的一种离子通道(ANO1)拮抗剂阻断。由血小板衍生生长因子受体α(PDGFRα)细胞转导的嘌呤能神经传递如何影响ICC中的ANO1尚不清楚。我们比较了近端和远端结肠的神经反应。刺激后反应在近端结肠中可通过抑制一氧化氮能神经传递而被阻断,但P2Y1受体拮抗剂在远端结肠中更有效。通过电压依赖性通道(Ca3)的钙内流增强了ICC中的钙释放。因此,我们推测,与ICC电耦合的PDGFRα细胞中嘌呤能反应引起的超极化可能会减少Ca3通道的失活,并在抑制性反应停止时通过阳极断裂激活钙进入ICC。远端结肠中的刺激后反应被MRS2500(P2Y1受体拮抗剂)、蜂毒明肽(SK通道拮抗剂)和NNC55 - 0396(Ca3拮抗剂)阻断。这些化合物也阻断了结肠中部和远端的传播性收缩。这些数据首次明确证明,平滑肌 - ICC - PDGFRα细胞(SIP)合体中的功能整合产生了一种主要的运动行为。要点:由肠神经系统引发的传播性推进性收缩是结肠中的一种主要运动行为。推进性收缩所必需的收缩的一个主要组成部分发生在肠内抑制性神经传递停止时(刺激后反应),并由与平滑肌细胞电耦合的Cajal间质细胞(ICC)产生。肠内抑制性神经传递的性质从近端结肠(主要由一氧化氮引起)转变为远端结肠(主要由嘌呤神经递质引起)。结肠中不同的细胞转导一氧化氮和嘌呤。ICC转导一氧化氮,但另一种间质细胞类型,即PDGFRα细胞,转导来自嘌呤能神经元的输入。然而,近端和远端结肠中的刺激后反应仍在ICC中产生。本文探讨了ICC、PDGFRα细胞和平滑肌细胞的整合行为如何在结肠中实现推进性运动。