1. Kosterlitz Centre for Therapeutics, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD Scotland, U.K.
2. Department of Pharmacology & Toxicology, University of Toronto, Toronto M5S 1A8, Canada
3. Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen, AB24 3UE Scotland, U.K.
4. C.N.R. − I.C.R.M., via Mancinelli 7, 20131 Milan, Italy