1. Division of Nuclear Medicine, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
2. Division of Radiation Health Sciences, Department of Environmental Health Sciences, Johns Hopkins University School of Hygiene and Public Health, Baltimore, MD 21205.
3. Department of Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
4. University of Maryland Psychiatric Research Center, Baltimore, MD 21201.
5. National Institute of Drug Abuse, Addiction Research Center, Baltimore, MD 21224
6. Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
7. Division of Neuroradiology, Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
8. Departments of Neuroscience, Pharmacolopy and Molecular Science, and Psychiatry, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
9. Medical Physiology Department A, Panum Institute, Copenhagen University, Copenhagen, Denmark 2200.