1. Molecular Neurobiology Laboratory (151), Veterans Administration Medical Center, Minneapolis, MN 55417, USA.
2. Department of Psychiatry, University of Minnesota, Minneapolis, MN 55455, USA.
3. Departments of Cell Biology, Medicine, and Surgery, Duke University Medical Center, Durham, NC 27710, USA.
4. Departments of Anatomy and Physiology and the W. M. Keck Foundation Center for Integrative Neuroscience, University of California, San Francisco, CA 94143, USA.
5. Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.