1. The Salk Institute for Biological Studies, La Jolla, California.
2. Howard Hughes Medical Institute, La Jolla, California.
3. Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
4. Neurosciences Unit, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal.
5. Division of Biology, University of California San Diego, La Jolla, California.