1. Neurosciences Research, SmithKline Beecham Pharmaceuticals, Third Avenue, Harlow CM19 5AW
2. Herchel Smith Laboratory for Medicinal Chemistry, University of Cambridge School of Clinical Medicine, University Forvie Site, Robinson Way, Cambridge CB2 2PZ, UK
3. Physiological Laboratory, University of Cambridge, Downing Street, Cambridge CB2 3EG,