1. Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden;
2. Department of Anatomy and Physiology, University of Padua, Padua, Italy;
3. National Institute on Drug Abuse, NIH, DHHS, Baltimore, Maryland; and
4. Department of BioMedical Sciences, University of Modena, Modena, and IRCCS Lido, Venice, Italy