In cold CRPS patients, an imbalance between the vasodilator NO and the vasoconstrictor endothelin-1 (ET-1) in artificial blisters on the skin of the affected extremity has been demonstrated (Groeneweg et al., 2006); evidence that advised about the role of endothelial dysfunction linked to aberrant inflammatory responses in CRPS vasomotor disturbances (Groeneweg et al., 2008, 2009). Here, EDN1 is linked to complex regional pain syndrome.