Effects of dipyridamole, nitroglycerin, and nitroprusside on coronary vascular resistance in rabbits: measurement with pulsed Doppler velocimetry.

ABSTRACT

Dipyridamole, nitroglycerin, and nitroprusside are all effective vasodilators. However, few studies have compared their in vivo coronary vasodilatation effects. The purpose of this study was to compare the effects of these agents on coronary blood flow velocity and vascular resistance in anesthetized, open-chest rabbits. Male New Zealand white rabbits were anesthetized, and a 3-mm, suction-type, pulsed Doppler velocimeter probe was applied to the proximal part of the left anterior descending coronary artery after median sternotomy. The rabbits received infusion of various doses of dipyridamole (0.1 mg/kg, n = 5; 1 mg/kg, n = 5; 10 mg/kg, n = 9), nitroglycerin (0.01 mg/kg, n = 8; 0.1 mg/kg, n = 5; 1 mg/kg, n = 5; 10 mg/kg, n = 7), or nitroprusside (0.01 mg/kg, n = 5; 0.1 mg/kg, n = 5; 1 mg/kg, n = 5). The percent changes in coronary blood flow velocity and coronary vascular resistance were measured. All three vasodilators increased coronary blood flow velocity significantly and decreased coronary vascular resistance dose-dependently. The dose-response curves of dipyridamole, nitroglycerin, and nitroprusside were significantly different from one another (p < 0.01). Dipyridamole at a dose of 10 mg/kg produced the greatest increase in coronary blood flow velocity and the greatest reduction in coronary vascular resistance in anesthetized, open-chest rabbits.