1. From the Departments of Pharmacology (K.Q., C.P.L.H.C., P.K.M., P.T.-H.W.) and Biochemistry (B.H.), Yong Loo Lin School of Medicine, National University of Singapore, Kent Ridge, Singapore; and Department of Neurology (C.P.L.H.C.), National Neuroscience Institute, Singapore General Hospital Campus, Singapore General Hospital.