〔Abstract〕 Objective To investigate whether fenoldopam(FNDP)(an agonist of type 1 dopamine receptor) has a protective effect on thoracic aortic aneurysm(TAA) in mice.Methods Three-week-old male C57BL/6J mice were treated with β-aminopropionitrile(BAPN) to induce TAA.The mice were divided into three groups:the control group,the BAPN group,and the BAPN+FNDP group(FNDP injected intraperitoneally).The incidence and survival rate of TAA were recorded.Gross anatomy of the whole aortae was observed.Elastin staining was performed to assess morphological change,while immunohistochemistry was employed to evaluate the expressions of matrix metalloproteinase 2(MMP2),matrix metalloproteinase 9(MMP9) and cluster of differentiation 68(CD68)respectively.Gelatin zymography was conducted to assess MMP2 and MMP9 activity.Reverse transcription-polymerase chain reaction(RT-PCR) was performed to measure the mRNA expression levels of dopamine receptor D1(D1DR),dopamine receptor d2(D2DR),dopamine receptor d3(D3DR),dopamine receptor d5(D5DR),interleukin-1β(IL-1β),interleukin-6(IL-6),tumour necrosis factor-α(TNF-α),monocyte chemoattractant protein-1(MCP-1),alpha-smooth muscle actin(α-SMA) and smooth muscle protein 22-alpha(SM22α).Results Compared to the control group,the BAPN group exhibited significant formation of TAA.Elastic fiber disruption was also observed in the thoracic aortic wall,along with a significant decrease in the mRNA levels of D1DR and D5DR.The BAPN+FNDP group showed a significant reduction in the incidence of TAA formation and the rate of aneurysm rupture compared to the BAPN group.The disruption and rupture of elastic fibers in the thoracic aortic wall were significantly improved in the BAPN+FNDP group.The levels of MMP2 and MMP9 in the thoracic aortic wall significantly decreased,and the enzymatic activity of MMP2 in the serum was significantly reduced.Moreover,macrophage infiltration in the thoracic aortic wall was significantly reduced and the mRNA levels of IL-1β,IL-6,TNF-α and MCP-1 also significantly decreased after FNDP treatment.There was no statistically significant difference in the mRNA levels of α-SMA and SM22α.Conclusion FNDP shows an inhibitory effect on TAA progression in mice,suggesting a potential of FNDP as a therapeutic agent for TAA.