1. From the Department of Experimental and Clinical Medicine, Pharmacology Unit and Institute of Surgery, University of Ferrara (C.E., M.F., D.P., D.R., P.G.), and the Institute of Internal Medicine, University of Sassari and National Institute of Biostructure and Biosystems, Osilo, Sassari (P.M.), Italy; and the Departments of Surgery and Physiology, University of California at San Francisco (E.F.G., N.W.B.).