Abstract: The aim of this research is to see the effect of intra-arterial infusion of leptin on blood pressure of salt loaded rabbits in vivo. Increased blood pressure was produced in rabbits by giving diets containing 8% sodium chloride for 5 weeks. Leptin in different concentrations was infused intra-arterially into rabbits fed on high salt diets and the response was compared in rabbits fed with low salt diets. High salt diets produced significant increase in blood pressure. In rabbits fed with low salt diet, leptin infused intra-arterially caused an increase in blood pressure while infusion of leptin into rabbits fed with high salt diets does not affect the blood pressure. In conclusion, salt loading to rabbits abolishes the effect of leptin on cardiovascular system. This may indicate that leptin effect on sympathetic activity is altered by high salt diets in these animals.