The present invention provides a screening tool andscreening method for obtaining a substance useful as aprophylactic and/or therapeutic drug for diseases associatedwith 5-HT production/secretion abnormalities, includingdigestive organ diseases, and a prophylactic and/ortherapeutic drug for diseases associated with 5-HTproduction/secretion abnormalities, including digestive organdiseases. Examples of digestive organ diseases in the presentinvention include constipation type irritable bowel syndrome,functional dyspepsia, constipation, diarrhea type irritablebowel syndrome, diarrhea and vomiting.
