1. Department of Anesthesiology, The Center for the Study of Itch; Washington University School of Medicine; St. Louis MO 63110 USA
2. Department of Integrative Medicine and Neurobiology, State Key Laboratory of Medical Neurobiology; Shanghai Medical College, Fudan University; Shanghai 200032 China
3. Department of Internal Medicine; Washington University School of Medicine; St. Louis MO 63110 USA