摘要Background Konjac oligosaccharide(KOS),which is produced through the degradation of konjac glucomannan via enzy-matic,chemical,or physical treatments,has been found to have laxative effects.The current study aimed to elucidate the mechanisms underlying the laxative effect of KOS.Methods KOS was administered by gavage to wild-type and 5-hydroxytryptamine 4 receptor(5-HT4R)-knockout C57BL/6 mice subjected to loperamide-induced constipation for four weeks.Following treatment,feces,blood,small intestine,colonic tissue,and intestinal contents were collected.Constipation-related parameters,gastrointestinal hormones,and Ca2+con-centrations were evaluated.Histopathological changes were examined via hematoxylin and eosin staining.Immunofluores-cence staining,Western blotting,and immunohistochemical staining were performed to detect the 5-HT4R/cyclic adenosine monophosphate(cAMP)/protein kinase A(PKA)pathway.Isolated smooth muscle cells(SMCs)were treated with KOS and GR113808(a 5-HT4R antagonist),morphologically observed under an inverted microscope,and identified by α-SMA immunofluorescence staining.Cell viability was assessed via CCK-8 assays.5-HT4R/cAMP/PKA/p-CREB pathway activity in SMCs was detected via Western blotting.Results KOS alleviated loperamide-induced constipation in mice.KOS activated the 5-HT4R/cAMP/PKA/p-CREB pathway in loperamide-induced constipated mice.The protective effect of KOS was significantly diminished in 5-HT4R-/-mice.KOS promoted the proliferation of SMCs by activating the 5-HT4R/cAMP/PKA/p-CREB signaling pathway.Conclusion KOS improves loperamide-induced constipation by activating the 5-HT4R/cAMP/PKA/p-CREB signaling pathway.