1. Center for Clinical Pharmacology, University of Health Sciences & Pharmacy at St. Louis and Washington University School of Medicine, St. Louis, Missouri 63110, United States
2. Department of Anesthesiology and Washington University Pain Center, Washington University School of Medicine, St. Louis, Missouri 63110, United States
3. Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, California 94158, United States
4. Department of Computer Science, Stanford University, Stanford, California 94305, United States
5. Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, United States
6. Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, California 94305, United States
7. Department of Pharmacodynamics, University of Florida, Gainesville, Florida 032610, United States