Objective To explore the intervention mechanism of Changzhou Tongbian Formula on functional constipation(FC)combined with depression in rats.Methods A rat model of FC combined with depressive-like behaviors was established by using gastric gavage of berberine hydrochloride and chronic unpredictable mild stress.The model rats were randomly divided into blank group,model group,lactulose group,and Changzhou Tongbian Formula high-,medium-,and low-dose groups,and the intervention was carried out for five weeks.The fecal water content was calculated before and after intervention.The small intestinal propulsion rate was calculated after intervention.The depressive-like behavior levels of rats were evaluated by forced swimming test and sucrose preference test before and after intervention.The colonic mucosal morphology was observed by HE staining.The morphology and number of pyramidal cells in the hippocampal CA1 and DG regions were observed by Nissl staining.The relative protein expression levels of the transient receptor potential vanilloid 4(TRPV4)in colonic tissue,as well as brain-derived neurotrophic factor(BDNF),tyrosine kinase receptor B(TrkB),mitogen-activated protein kinase(MAPK),and cAMP-response element binding protein(CREB)in the hippocampus of rats in each group were detected by Western Blot method.Results Compared with the blank group,the fecal water content of rats in the model group was significantly reduced(P＜0.001),the small intestinal propulsion rate was significantly lower(P＜0.01),the sucrose preference index was significantly decreased(P＜0.001),the number of pyramidal cells in the CA1 and DG regions of the hippocampus was significantly reduced(P＜0.001),and the TRPV4 in the colon and the BDNF,TrkB,MAPK,and CREB protein contents in the hippocampus were all significantly decreased(all P＜0.001).Compared with the model group,the fecal water content of the Changzhou Tongbian Formula high-,midium-,low-dose groups and the lactulose group were significantly increased(P＜0.001,P＜0.01).The small intestinal propulsion rate of the Changzhou Tongbian Formula high-,low-dose groups and lactulose group were significantly increased(P＜0.01,P＜0.05).The sucrose preference indices of the Changzhou Tongbian Formula high-,midium-,low-dose groups and lactulose group were significantly increased(P＜0.01,P＜0.05).There was no abnormality in the colonic histology.The numbers of pyramidal cells in the CA1 and DG regions of the hippocampus of the Changzhou Tongbian Formula high-,midium-,low-dose groups and lactulose group were significantly increased(P＜0.01,P＜0.001).The TRPV4 content in the colon of the Changzhou Tongbian Formula high-,midium-,low-dose groups and lactulose group were significantly increased(P＜0.001),and the BDNF,TrkB,MAPK,and CREB protein contents in the hippocampus were all significantly increased(P＜0.05,P＜0.01,P＜0.001).Conclusion After intervention,Changzhou Tongbian Formula can significantly improve the TRPV4 content in the colon of model rats with the comorbidity of FC with depression,increase the moisture content of feces,promote intestinal peristalsis and improve constipation.Meanwhile,TRPV4 can activate the BDNF/TrkB/MAPK pathway,trigger an increase in downstream CREB,improve neuroplasticity and thus alleviate some depressive-like behavior.