1. W. A. Carlezon Jr., J. Thome, V. G. Olson, S. B. Lane-Ladd, E. S. Brodkin, N. Hiroi, R. S. Duman, E. J. Nestler, Division of Molecular Psychiatry, Center for Genes and Behavior, Yale University School of Medicine and Connecticut Mental Health Center, 34 Park Street, New Haven, CT 06508, USA. R. L. Neve, Department of Genetics, Harvard Medical School, McLean Hospital, 115 Mill Street, Belmont, MA 02178, USA.