The aim of this study was to investigate the effect of naloxone (IV or IM administration) and
methylnaltrexone (subcutaneous administration) on esophageal sensitivity, in a group of
healthy volunteers in order to evaluate the role of endogenous opiods in symptom perception
in gastro-esophageal reflux disease. Esophageal sensitivity was assessed by using a
multimodal esophageal stimulation protocol where sensitivity to thermal, mechanical,
electrical and chemical stimulation was tested.