1. Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona, E-08028, Spain, National Institute on Drug Abuse, Intramural Research Program, NIH, Department of Health and Human Services, Baltimore, Maryland 21224, Max-Delbrück-Center for Molecular Medicine, D-13092 Berlin-Buch, Germany, Department of Neuroscience, Division of Cellular and Molecular Neurochemistry, Karolinska Institutet, S-171 77 Stockholm, Sweden, and Section of Physiology, Department of Biomedical Sciences,...