1. Department of Neurosurgery Johns Hopkins School of Medicine Baltimore MD 21205 U.S.A.
2. Department of Biological Chemistry Johns Hopkins School of Medicine Baltimore MD 21205 U.S.A.
3. Solomon H. Snyder Department of Neuroscience Neurosurgery Pain Research Institute Johns Hopkins School of Medicine Baltimore MD 21205 U.S.A.
4. Department of Cell and Developmental Biology University of Michigan Medical School Ann Arbor MI 48109 U.S.A.
5. Department of Dermatology University of Michigan Medical School Ann Arbor MI 48109 U.S.A.
6. Department of Neurology Johns Hopkins School of Medicine Baltimore MD 21205 U.S.A.