Small doses of four drugs-bradykinin, sodium nitroprusside, miconazole, and LNMMA-will be given through the arterial catheter. Bradykinin stimulates the release of EDHF and can lower blood pressure. Sodium nitroprusside causes blood vessels to dilate and is used to treat high blood pressure and heart failure. Miconazole is commonly prescribed to treat various infections, including vaginal yeast infections, jock itch and athlete's foot. In much higher doses, it is used to treat fungal infections that have spread to the lungs, brain, kidneys, or bladder. LNMMA inhibits production of nitric oxide, another substance produced by the lining cells of blood vessels.