The effect of acetylcholine on blood pressure is primarily a dilating effect, causing a transient decrease in blood pressure due to the ability to dilate blood vessels throughout the body. The dilated vessels include the pulmonary and coronary arteries, and the vasodilating effect is mainly through agonism of the M-choline receptor subtype of vascular endothelial cells, leading to the release of nitric oxide and causing relaxation of smooth muscle cells, which leads to a decrease in blood pressure. It may also be caused reflexively by pressure receptors or chemoreceptors. If the vascular endothelium is injured, the effect of acetylcholine is not present. Acetylcholine has a slowing and myocardial contractile effect, which can cause a significant decrease in myocardial blood displacement, resulting in a decrease in blood pressure.