<prompt> All of the following are obligate coronary vasodilators except:NitroglycerineNitric oxideHypoxia and HypercapniaAcetylcholine  <response>: All are known to cause vasodilatation.Only acetylcholine can also be a vasoconstrictor if the endothelium is dysfunctional or absent and nitric oxide can not be produced. In that case it is not an obligate vasodilator. 