Footnotes

• JM and TM contributed equally.

• Acknowledgements The authors are grateful to Professor Dr Rolf Graf (Department of Visceral and Transplantation Surgery, University Hospital, Zurich, Switzerland) and to Professor Dr Michael Bader (Max-Delbrück-Center for Molecular Medicine, Berlin, Germany) for providing us the TPH1^−/− mice.

• Contributors JM, TM and PP performed the fluorescence and fluid secretion measurements. AB, VV and ZR were involved in the study design and in the interpretation of the results. PH was the supervisor of the study and had full access to all results during this research project. The manuscript was drafted by PH.

• Funding Our work was supported by the MTA-SZTE Momentum Grant (LP2014-10/2014) and the National Scientific Research Found grant K109756.

• Competing interests None declared.

• Provenance and peer review Not commissioned; internally peer reviewed.

• Data sharing statement All results of the study have been included to the manuscript and no other persons, besides the authors, had access to the results.