Consistently, acutely increasing serotonergic activity with the selective serotonin reuptake inhibitor showed no effect on rectal motor function.55,56 In addition, serotonin was found to elevate aquaporin-3 expression in the colon using a morphine-induced constipation, we also found decreased faecal water content and shrinking number of ICC in aged mice, suggesting that altered 5-HT signalling as a crucial driver to defecation problem in the aged. This evidence concerns the gene AQP3 and intrahepatic cholangiocarcinoma.