1. Department of Medicinal Chemistry, Division of Organic Pharmaceutical Chemistry, Uppsala University, P.O. Box 574, SE-751 23 Uppsala, Sweden, Service of Endocrinology, Faculty of Medicine, University of Sherbrooke, Sherbrooke J1H 5N4, Quebec, Canada, Department of Pharmaceutical Sciences, Division of Biological Research on Drug Dependence, Uppsala University, P.O. Box 591, SE-751 24 Uppsala, Sweden, and Department of Chemistry, Organic Chemistry, Uppsala University, P.O. Box 599, SE-751 24 Uppsala, Sweden