1. From the Department of Pharmacology and Toxicology (C.B.A., A.M.M., and R.D.R.), Medical College of Georgia, Augusta; the Vascular Biology Center (M.I.A., J.M.O., J.C.S., and D.W.S.), Medical College of Georgia, Augusta; and the Department of Physiology (D.W.S.), Medical College of Georgia, Augusta.