1. From the Cellular and Molecular Physiology Laboratory, Department of Physiology (J.P., C.F., C.A., M.I.R., P.C., L.S.), the Department of Pharmacology (M.I.R.), Faculty of Biological Sciences, and the Department of Obstetrics and Gynecology (P.C.), Faculty of Medicine, University of Concepción, Concepción, Chile.