1. Laboratory of Medicinal Chemistry, Natural and Synthetic Drugs Research Center, University of Liège, avenue de l'Hôpital, 1 (B36), Laboratory of Pharmacology, Research Center for Cellular and Molecular Neurobiology, University of Liège, avenue de l'Hôpital, 3 (B23), and Laboratory of Physiology, University of Liège, avenue de l'Hôpital, 3 (B23), B-4000 Liège 1, Belgium