The product of EDNRA, endothelin receptor A, is a G protein-coupled receptor that causes cellular proliferation and contraction (26, 27) of smooth muscle when ligated to endothelin. Polymorphisms in this gene have been associated with variation in vascular phenotypes stemming from vasoconstriction.This gene encodes the receptor for endothelin-1, a peptide that plays a role in potent and long-lasting vasoconstriction. This receptor associates with guanine-nucleotide-binding (G) proteins, and this coupling activates a phosphatidylinositol-calcium second messenger system. Polymorphisms in this gene have been linked to migraine headache resistance. Alternative splicing results in multiple transcript variants.