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相关概念视频

G-Protein Gated Ion Channels01:21

G-Protein Gated Ion Channels

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GPCRs are primarily responsible for our sense of smell, taste, and vision.  The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory...
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GPCRs Regulate Adenylyl Cylase Activity01:09

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Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of...
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Cholinergic Receptors: Muscarinic01:25

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The pharmacological actions of acetylcholine are elicited via its binding to two families of cholinergic receptors or cholinoceptors, namely, muscarinic and nicotinic receptors. Muscarinic receptors are G protein-coupled receptors and have five subtypes, M1–M5. All mAChR subtypes are activated by acetylcholine and blocked by the antagonist, atropine. 
The subtypes M1, M3, and M5 couple with the Gq subunit and activate the phospholipase C (PLC) activity, mobilizing intracellular Ca2+....
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Mechanism of Cardiac Arrhythmias01:28

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Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
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Antiarrhythmic Drugs: Class I Agents as Sodium Channel Blockers01:22

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Class I antiarrhythmic drugs are used to treat various types of arrhythmias or irregular heart rhythms. These drugs block the sodium (Na+) channels in the cardiac cells, thereby affecting the movement of electrical impulses across the heart. Class I antiarrhythmic drugs are divided into three subgroups: Class IA, Class IB, and Class IC, each with distinct mechanisms of action and effects on the heart.
Class 1A Antiarrhythmic Drugs: These drugs work by moderately blocking sodium channels,...
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Antiarrhythmic Drugs: Class III Agents as Potassium Channel Blockers01:12

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Class III antiarrhythmic drugs are a group of medications that can prolong action potentials in the heart. They achieve this by blocking potassium channels or enhancing inward currents from sodium channels. However, these drugs have a unique property of "reverse use-dependence," which is most pronounced at slower heart rates and can lead to torsades de pointes—a specific type of arrhythmia. However, it is essential to note that excessive QT interval prolongation—a measure of...
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相关实验视频

Updated: May 5, 2026

Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes
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Isolation and Kv Channel Recordings in Murine Atrial and Ventricular Cardiomyocytes

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在人类慢性心房中,G蛋白结合内向整正K+) 电流 (IK,ACh) 的下调的分子基础:GIRK4 mRNA的下降与IK,ACh的减少以及肌受体介导的动作潜力的缩短有关.

D Dobrev1, E Graf, E Wettwer

  • 1Department of Pharmacology, University of Technology, Dresden, Germany. dobrev@rcs.urz.tu-dresden.de

Circulation
|November 21, 2001
PubMed
概括

人类的慢性心房 (AF) 降低了G蛋白合的向内调整的K+电流 (IK,ACh) 的调节,并提高了向内调整的K+电流 (IK1) 的调节. 在AF中的这种电力改造使肌细胞适应高速率.

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科学领域:

  • 心脏病学 心脏病学
  • 电子生理学 电子生理学
  • 分子生物学分子生物学

背景情况:

  • 副交感神经系统与心房动 (AF) 病变发生有关.
  • 在慢性AF中,G蛋白结合的向内调整K ((+) 电流 (I ((K,ACh)) 的作用尚不清楚.

研究的目的:

  • 调查慢性AF患者在人类心房肌细胞中的I(K,ACh) 和其GIRK4亚单元的变化.
  • 检查AF中变异离子电流的功能相关性.

主要方法:

  • 隔离的人类心房肌细胞中的电生理学记录.
  • 使用竞争性逆转录聚合酶链反应,对GIRK4和Kir2.1mRNA水平进行定量分析.
  • 评估动作潜力的持续时间和对肌肉蛋白受体刺激的反应.

主要成果:

  • 在AF肌细胞中,I(K,ACh) 密度降低了约50%,GIRK4 mRNA减少.
  • 在AF中,向内调整的K ((+) 电流 (I ((K1)) 密度翻了一番,并增加了Kir2.1 mRNA.
  • 动作潜力的持续时间在AF中减少,肌肉蛋白受体介导的缩短减弱.

结论:

  • 慢性AF导致人类心房中I(K1) 的转录上调和I(K,ACh) 的下调.
  • 这些离子通道的变化减弱了肌肉类受体对作用潜力的影响.
  • 耳前肌细胞下调I ((K,ACh) 以适应慢性高速率,抵消电力重塑效应.