1. Department of Chemistry, Gonda-Goldschmied Center, Bar-Ilan University, Ramat-Gan 52900, Israel, Institute of Neurobiochemistry, Faculty of Medicine, Otto von Guericke University, Leipziger Strasse 44, D-39120 Magdeburg, Germany, and Department of Pharmacology, University of North Carolina, School of Medicine, Chapel Hill, North Carolina 27599