1. University of Paris 6, University of Paris 5, Institut National de la Santé et de la Recherche Médicale UMRS 1138, Centre National de la Recherche Scientifique ERL 8228, Centre de Recherche des Cordeliers, Paris, France;
2. Institute of Physiology University of Regensburg, Regensburg, Germany;
3. Departments of Medicine and Pharmacology, University of California, San Diego, La Jolla, California, and San Diego Veterans Affairs Healthcare System, San Diego, California; and
4. Department of Mathematics, Duke University, Durham, North Carolina