1. Oklahoma Center for Neuroscience University of Oklahoma Health Sciences Center Oklahoma City OK USA
2. VA Health Care System Oklahoma City OK USA
3. Department of Neurology University of Oklahoma Health Sciences Center Oklahoma City OK USA
4. Department of Physiology University of Oklahoma Health Sciences Center Oklahoma City OK USA
5. Centre for Digestive Diseases Blizard Institute of Cell & Molecular Science Wingate Institute of Neurogastroenterology Barts and the London School of Medicine & Dentistry Queen Mary University of London London UK
6. Institute of Applied Clinical Sciences University of Keele Keele UK
7. Department of Anesthesiology and Perioperative Medicine University of Alabama at Birmingham Birmingham AL USA