1. Cell Signalling Research Group, Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, U.K.
2. Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, U.K.
3. School of Pharmacy and Centre for Biomedical Sciences, University of Nottingham, Nottingham, NG7 2RD, U.K.