This research study is being done to compare the effects of Aprepitant and placebo on fasting gastric volume, accommodation volume, satiation (fullness) and gastric emptying.

Inclusion criteria:

1. Able to provide written consent
2. No medical problems or chronic diseases, specifically, no type 2 diabetes mellitus
3. Body Mass Index of 18-35 kg/m^2
4. Female subjects must have negative urine pregnancy tests and must not be lactating prior to receiving study medication and radiation exposure
5. For females able to bear children, a hormonal (i.e., oral, implantable, or injectable) and single-barrier method, or a double-barrier method of birth control must be used throughout the study
6. Female subjects unable to bear children must have this documented in the medical record (i.e., tubal ligation, hysterectomy, or post-menopausal [defined as a minimum of one year since the last menstrual period])

Exclusion criteria:

1. Diagnosis of gastrointestinal diseases

2. Structural or metabolic diseases that affect the gastrointestinal system

3. Unable to avoid the following over-the-counter medications 48 hours prior to the baseline period and throughout the study:

   • Medications that alter GI transit including laxatives, magnesium and aluminum containing antacids, prokinetics, erythromycin
   • Analgesic drugs including NSAIDs and cyclooxygenase-2 (COX-2) inhibitor. (NOTE: Stable doses of thyroid replacement, estrogen replacement, low-dose aspirin for cardioprotection, and birth control (but with adequate backup contraception as drug-interactions with birth control have not been conducted) are permissible.)

4. History of recent surgery (within 60 days of screening).

5. Acute or chronic illness or history of illness, which in the opinion of the investigator could pose a threat or harm to the subject or obscure interpretation of laboratory test results or interpretation of study data such as frequent angina, Class III or IV congestive heart failure, moderate impairment of renal or hepatic function, poorly controlled diabetes, etc.

6. Any clinically significant abnormalities on physical examination or laboratory abnormalities identified in the medical record, as determined by the investigator.

7. Acute GI illness within 48 hours of initiation of the baseline period.

8. Females who are pregnant or breastfeeding.

9. History of excessive alcohol use or substance abuse.

10. Participation in an investigational study within the 30 days prior to dosing in the present study.

11. Any other reason, which in the opinion of the investigator would confound proper interpretation of the study.