Abstract: OBJECTIVE To investigate long-term treatment effect of Danhong injection(DHI) on vasodilation in normal rats. METHODS Twenty normal male SD rats were divided into two groups randomly, DHI group and control group. We performed continuous intravenous administration during 28 days, and diastolic function of DHI in rats was detected by Ach and SNP. By applying Griess reagent kit/ELISA kit, checked the serum contents of nitric oxide(NO)/epoprostenol(PGI₂) in rats. Additionally, real time PCR(RT-PCR) was carried out to monitor the gene expression change of ACs, cAMP and PKAs in each group. RESULTS Compared with control group, DHI long-term treatment could significantly increase rats' vasodilation in response to ACh stimulation. However, it didn't exhibit close association with SNP stimulation. Moreover, DHI long-term treatment would increase PGI₂ level in serum without an impact on NO in serum. Meanwhile, RT-PCR showed that the expression of ACs, cAMP and PKAs in DHI group were up-regulated by 1.21, 1.78 and 1.48 times, respectively. CONCLUSION DHI long-term treatment can significantly improve endothelial-dependent vasodilation in rats by interfering ACs/cAMP/PKAs signal pathway mediated by PGI₂.