Abstract: OBJECTIVE  To observe the effects of Zhizhu Decoction on 5-HT₄R、CaM、MLCK in colon tissue of rats with slow transit constipation (STC).METHODS  Rats were divided into normal group, model group, Zhizhu Decoction group and positive (prucalopride) group, with 10 rats in each group. STC rats replicated by intragastric administration with compound diphenoxylate tablets. After modeling, Zhizhu Decoction and prucalopride were given, respectively, to corresponding groups by gavage. Water content of feces, the percentage of pushing carbonic powder, mRNA and protein contents of 5-HT₄R, CaM and MLCK in colon tissues of different groups were detected.RESULTS  Compared with the normal group, the water content of feces and the percentage of pushing carbonic powder in model group significantly decreased (P < 0.05, P < 0.01), the mRNA and protein contents of 5-HT₄R, CaM and MLCK in colon tissues also significantly decreased (P < 0.01). Compared with model group, water content of feces and percentage of pushing carbonic powder in Zhizhu Decoction group and positive group significantly increased (P < 0.05), and the mRNA and protein expressions of 5-HT₄R, CaM and MLCK in colon tissues also significantly increased (P < 0.05, P < 0.01). The data had no statistical significance between the Zhizhu Decoction group and the positive group (P>0.05).CONCLUSION  Zhizhu Decoction can improve the symptoms of STC, which may be related to promoting high expression of 5-HT₄R in colon tissue of rats to active the CaM-MLCK signaling pathway.