1. Department of Pharmacology, The University of Michigan Medical School, Ann Arbor, Michigan 48109, Department of Pharmacology, University of South Alabama, Mobile, Alabama 36688, Faculté de Pharmacie, UMR 862 CNRS, Pharmacologie Cellulaire, 5 rue Jean-Baptiste Clément, Chatenay-Malabry Cedex, France, and Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, People's Republic of China