1. From the Departments of Pharmacology (J.L.G., S.P., D.R.D., C.D.S.), Internal Medicine (J.L.G., M.E.D., E.J.B., C.D.S.), and Molecular Physiology and Biophysics (C.D.S.), Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa.