Abstract: AIM: To investigate the effect of ghrelin on the cardiovascular system. METHODS: 40 male Sprague-Dawley (SD) rats were randomized into control group and four drug groups with five rats in each group. After the rats were anesthetized, a microcatheter was inserted into the left ventricle through the right carotid artery, and left ventricular developed pressure (LVDP), maximal velocity of left ventricular pressure development and decline (+LV dP/dtmax and -LV dp/dtmax) and heart rate (HR) were recorded by a biological signal collecting system. Simultaneously, mean arterial blood pressure (MABP) was measured by right femoral artery intubation. The rats were given either ghrelin (1×10-7-1×10-4 g/kg) or saline and MABP and left ventricular indexes were observed for 30 min. Contractile function of the myocytes were detected. RESULTS: No obvious changes of MABP were observed in control group after injection of saline. Intravenous (i.v.) injection of ghrelin decreased MABP in a dose-dependent manner by 11.4%, 15.8% and 27.1%, respectively, in 10-6 g/kg, 10-5 g/kg and 10-4 g/kg groups. No significant difference was observed in LVDP, +dp/dtmax, -dp/dtmax and HR 30 min after i.v. injection of ghrelin. The PTA ±dL/dtmax were significancly decreased in the GRL groups compared with the control group. CONCLUSION: Ghrelin decreases MABP of rats and contractile function of ventricular myocytes in a dose-dependent manner.