Muscarinic acetylcholine receptor M2

The muscarinic acetylcholine receptor M2, also known as the cholinergic receptor, muscarinic 2, is a muscarinic acetylcholine receptor.

Function
The M2 muscarinic receptors are located in the heart, where they act to slow the heart rate down to normal sinus rhythm after stimulatory actions of the sympathetic nervous system, by slowing the speed of depolarization. They also reduce contractile forces of the atrial cardiac muscle, and reduce conduction velocity of the atrioventricular node (AV node). However, they have no effect on the contractile forces of the ventricular muscle.

Mechanism
M2 muscarinic receptors act via a Gi type receptor, which causes a decrease in cAMP in the cell, generally leading to inhibitory-type effects.

In addition, they modulate muscarinic potassium channels. In the heart, this contributes to a decreased heart rate.

Gene
Muscarinic acetylcholine receptor M2 is encoded by the gene.