Objective:To investigate the role of 5-HT7 receptor in the pathogenesis of irritable bowel syndrome(IBS). Methods:Rat model of D-IBS was established by intracolonic instillation of acetic acid and restraint stress; Rat model of C-IBS was established by stomach irrigated with 0-4oC cool water daily for 14 d. The content and distribution of 5-HT7 receptor at the brain and bowel was examined by immunohistochemistry and the expression of 5-HT7 receptor mRNA was detected by fluorescence quantitative RT-PCR(Real-time PCR). Results:Immunocytochemistry result showed the 5-HT7 rceptor positive staining at hippocampus and hypothalamus of both C-IBS and D-IBS group was stronger than that of control group(P < 0.01). The 5-HT7R expression at ileum, proximate colon, distal colon of C-IBS group was significantly stronger than that of control group(P < 0.05). Realtime-PCR analysis results showed the expression level of 5-HT7 receptor at hippocampus and hypothalamus of both C-IBS and D-IBS group was increased than that of control group(P < 0.05). At proximal and distal colon of C-IBS group, the 5-HT7 receptor mRNA expression was increased compared with control group(P < 0.05). Conclusion:The up-regulated expression of 5-HT7 receptor at brain and colon may play an important role in the pathogenesis of C-IBS.