**3. Conclusion**

The effects of duodenal acidification by transnasal endoscopy significantly increased various dyspeptic symptoms not suppresses this symptoms. Further, this method enabled the evaluation of duodenal hypersensitivity to acid in healthy volunteers and in patients with FD. Using this method, we might be able to clarify a correlation between duodenal hypersensitivity to acid and the effectiveness of PPI therapy for the treatment of FD. A further examination is needed.
