How Acetylcholine Decreases Heart Rate?

Acetylcholine slows the heart rate by activating the M2 muscarinic receptor

Why does ACh decrease heart rate?

The binding of acetylcholine to M₂ receptors serves to slow heart rate till it reaches normal sinus rhythm. This is achieved by slowing the rate of depolarization, as well as by reducing the conduction velocity through the atrioventricular node.

How does acetylcholine decrease blood pressure?

Note: following administration of an i.v. bolus, acetylcholine will stimulate muscarinic receptors located on the vascular endothelium, resulting in the release of nitric oxide. Nitric oxide will relax arterial smooth muscle, resulting in a fall in arterial blood pressure.