 EDD experiments: EDD agonists are drugs than cause vasodilation to increase blood flow temporarily. We will use 4 different agonists to test EDD function from several perspectives. After control EDD agonist infusions, subjects will repeat EDD agonists under conditions of K channel inhibition, and again under K channels plus nitric oxide and prostaglandin inhibition. This last phase of the study is aimed at testing acute compensatoryredundant vasodilator mechanisms. These trials will involve infusion of endothelial agonists, with and without inhibition of specific vasodilatory mechanisms. Agonists include: ATP, Bradykinin BK, Isoproterenol ISO, and Acetylcholine Ach, will be infused 3 times each order randomized. Agonists will be infused under the following conditions: 1 Alone control 2 in combination with Barium Chloride BaCl2 3 in combination with BaCl2, L-N-monomethyl Arginine Acetate L-NMMA, and Ketorolac. EDD agonists each cause a temporary increase in forearm blood flow, which returns to baseline within minutes after infusion has stopped. Antagonists BaCl2, L-NMMA and ketorolac will likely reduce EDD responses to agonists, and may also reduce resting forearm blood flow or increase blood pressure e.g. L-NMMA may decrease forearm blood flow 30-50 an increase BP 5-10 mmHg. The entire EDD study visit will be 5 hours 1 hour setup and 4 hours experimental procedures. The EDD protocol is further described here: 