This study bases on the successfully completed project SNF 320000-112006 (EK 1152 and SwissMedic 2005dr2207e) and will document the physiological effects of inhibited gastric secretion on the volume as well as the acidity of gastric secretion by high dose proton pump inhibitors in GERD patients and healthy controls. Twelve participants in each group will be studied in a randomized, double-blind placebo controlled trial. A novel non-invasive MRI technique developed in Zurich will assess the volume of gastric secretion following the ingestion of a regular liquid meal. In addition, intragastric / esophageal pH monitoring will assess the link between volume and intragastric distribution of gastric secretion on reflux events and symptoms. In addition, the effect of gastric secretion on outcome parameters of a non-invasive stable isotope breath test for measurement of gastric emptying will be assessed.

Inclusion criteria: - Healthy volunteers must have less than one episode of reflux or dyspeptic symptoms per month of no more than mild severity in the last 3 months

- Reflux patients (GERD) must have chronic symptoms (>8 weeks) suggestive for GERD (definition and questionnaire see Appendix page 30). In addition, the initial screening manometry must show no severe esophageal dysmotility (e.g. spasm, achalasia). If in addition a pH-study has been performed the acid exposure must be > 4.2% / 24h.

Exclusion criteria: - Age under 18 or above 65

• Pathologic underweight or overweight (BMI < 18 or > 30 kg/m2)
• Previous history of gastrointestinal disease or surgery (excludes appendectomy, cholecystectomy, hernia repair and anorectal disorders)
• Previous cardiorespiratory (excludes arterial hypertension), hematologic, renal, atopic, alimentary or psychiatric disease, diabetes, drug or alcohol abuse
• Patient unable to stop medication that alters gut function for 72 hours prior to the study, including anticholinergics, prokinetics, proton-pump inhibitors, non-steroidal anti-inflammatory drugs
• Positive Helicobacter pylori status on 13C-Urea breath test
• Presence of metallic implants, devices or metallic foreign bodies
• Pregnancy and lactation (female patients of child bearing age will receive a pregnancy test prior to study)
• Female volunteers without adequate contraception for the duration of the study
• Involvement in any other clinical trial during the course of this trial, nor within a period of 30 days prior to its beginning or 30 days after its completion