Coronary vasodilatation is caused by

Refer kDT 7/e p536 It serves as a metabolic coupler between oxygen consumption andcoronary blood flow. ... Parasympathetic stimulation of the hea (i.e., vagal nerve activation) elicits modest coronary vasodilation(due to the direct effects of released acetylcholine on the coronaries). In some types of blood vessels, there is evidence that adenosine producesvasodilation through increases in cGMP, which leads to inhibition of calcium entry into the cells as well as opening of potassium channels. Incardiac tissue, adenosine binds to type 1 (A1) receptors, which are coupled to Gi-proteins.