1. Department of Pharmaceutical Sciences, University of Firenze, Via G. Capponi 9, 50121 Firenze, Italy, Department of Preclinical and Clinical Pharmacology, University of Firenze, Viale Pieraccini 6, 50139 Firenze, Italy, Department of Molecular and Functional Genomics, Synthélabo, 10 Rue des Carrîeres, 92500 Rueil-Malmaison, France, and Departments of Psychiatry, Neurobiology, Pharmacology, and Biotechnologies, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy