1. Departments of Cell and Molecular Biology, Northwestern University Medical School (L.M.S., E.M., M.H.-D.), Chicago, Illinois 60611
2. Department of Physiology and Biophysics, University of Illinois School of Medicine (D.B.H.), Chicago, Illinois 60611
3. Department of Pharmacology, Kumamoto University School of Medicine (E.M., H.Y.), 2-2-1 Honjo, Kumamoto 860-0811, Japan