Objective        To investigated the relationship of expression changes of transient receptor potential vanilloid 1 (TRPV1) and 5-hydroxytryptamine (5-HT) in rectal mucosa and rectal compliance in the patients with internal rectal prolapse (IRP).       Methods        A total of 20 out-patients who were diagnosed as IRP in our department and 20 sex- and age-matched healthy individuals for physical examination

from October to December 2012 were enrolled in this study. They received colonoscopy after anorectal manometry. Immunohistochemical assay for TRPV1 and 5-HT was carried out in the mucosal samples from the lower rectum at 4 cm above the dentate line.       Results        The initial sensation volume was significantly higher in IRP group than in normal control (

Z

=-3.710，

P

＜0.01)

but the largest feeling tolerance volume was obviously lower in IRP group (

Z

=-5.181

P

＜0.01). The rectal compliance was significantly lower in the IRP group than in normal control.TRPV1 was extensively expressed in the rectal mucosa of IRPs when compared in that of control (

Z

=-5.085

P

＜0.01). Similar expression was found in 5-HT in the rectal mucosa (

Z

=-4.734

P

＜0.01).       Conclusion        Rectal compliance in patients with IRP is significantly lower than normal control

which might be related with the significantly enhanced expression of TRPV1 and 5-HT in rectal mucosa which causes rectal hypersensitivity. It is may be one of the mechanisms of bowel dysfunction as anal bulge and frequent defecation in patients with internal rectal prolapse.