1. Department of Pharmaceutical Sciences, University of Firenze, Via U. Schiff 6, 50019 Sesto Fiorentino, Italy, Department of Molecular and Functional Genomics, Synthélabo, 10 rue des Carrîeres, 92500 Rueil-Malmaison, France, Department of Psychiatry, Neurobiology, Pharmacology e Biotechnologies, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy, and Department of Preclinical and Clinical Pharmacology, University of Firenze, Viale Pieraccini 6, 50139 Firenze, Italy