1. Washington University Pain Center and Department of Anesthesiology, Washington University in St. Louis, 660 S. Euclid Ave, Box 8054, 63110 St. Louis, MO, USA
2. Medical Scientist Training Program, Washington University in St. Louis, St. Louis, MO 63110, USA
3. Biotechnology Centre of Oslo, University of Oslo, Blindern N-0317, Oslo, Norway