1. Clinical Pharmacology and Digestive Pathophysiology Unit, Department of Clinical and Experimental Medicine, University of Parma, Maggiore University Hospital, Cattani Pavillon, I-43125 Parma, Italy
2. Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy
3. Clinic Hospital Lozano Blesa, University of Zaragoza, Zaragoza, Spain
4. Division of Gastroenterology, University of Washington, Seattle, WA, USA