Acetylcholine-sensitive muscarinic potassium channel (IK(ACh))

The acetylcholine-sensitive muscarinic potassium channel, often referred to as IK(ACh) or the muscarinic K+ channel, is a subtype of inwardly rectifying potassium channel present in cardiac tissues. Upon stimulation by acetylcholine via muscarinic M2 receptors, the channel opens through a G protein (especially Gi/o) βγ subunit-mediated pathway, markedly increasing potassium conductance across cardiac cell membranes. This process hyperpolarizes cardiac cells, particularly in the atrium and sinoatrial node, thereby slowing the heart rate and contributing to the parasympathetic regulation of cardiac rhythm. The channel can also be activated by adenosine and is susceptible to modulation by muscarinic agonists and antagonists. Dysfunction or inappropriate regulation of IK(ACh) can contribute to cardiac arrhythmias and diseases involving heart rate control[1][2][3].

Other names

Muscarinic K+ channelKACh channelIK(ACh)Acetylcholine-activated potassium channel

Activation: Acetylcholine binds to muscarinic M2 receptors, leading to βγ subunit dissociation from Gi/o proteins, directly gating and opening the GIRK (IK(ACh)) channel, resulting in increased K+ conductance and cell hyperpolarization[1][2]. Blockade: Muscarinic antagonists inhibit the M2 receptor, preventing channel activation and depolarizing cardiac pacemaker cells[1][2].