1. Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-12, Nishi-6, Kita-ku, Sapporo 060-0812, Japan, Department of Pharmacology, Tennis Court Road, University of Cambridge, Cambridge, CB2 1PD, U.K., and Wolfson Laboratory for Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath BA2 7AY, U.K.