1. Department of Medicinal Chemistry, BMC, Uppsala University, P.O. Box 574, SE-751 23 Uppsala, Sweden, Service of Endocrinology and Department of Physiology and Biophysics, Faculty of Medicine, University of Sherbrooke, Sherbrooke J1H 5N4 Quebec, Canada, Department of Gastrosurgical Research, Sahlgrenska Academy at Gothenburg University, SE-413 45 Gothenburg, Sweden, and Department of Biological Research on Drug Dependence, BMC, Uppsala University, P.O. Box 591, SE-751 23 Uppsala, Sweden