 Additional Inclusion criteria for the Multiple Ascending Dose study only: Must have symptoms suggestive of current gastroparesis or constipation as shown by any one or more of the following: 1. Need for regular use of prokinetics, laxatives, or stool softeners of any kind, 2. A total score of 2 or higher on the Gastroparesis Cardinal Symptoms Index total score equals average of scores on the 3 subscales, 3. A score of 5 or higher on the gastroparesis subscale or 5 or higher on the constipation subscale of the Gastrointestinal Symptoms in Neurodegenerative Disease Scale. 