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

Dipyridamole, nitroglycerin, and nitroprusside are all effective vasodilato rs. However, few studies have compared their in vivo coronary vasodilatatio n effects. The purpose of this study was to compare the effects of these ag ents on coronary blood now velocity and vascular resistance in anesthetized , open-chest rabbits. Male New Zealand white rabbits were anesthetized, and 3-mm, suction-type, pulsed Doppler velocimeter probe was applied to the pr oximal part of the left anterior descending coronary artery after median st ernotomy. The rabbits received infusion of various doses of dipyridamole (0 .1 nng/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 nitroprus side (0.01 mg/kg, n = 5; 0.1 mg/kg, n = 5 1 mg/kg ,n = 5). The percent chan ges in coronary blood flow velocity and coronary vascular resistance were m easured. All three vasodilators increased coronary blood flow velocity sign ificantly 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 ata dose of 10 mg/kg produced the greatest increase in coronary blood flow velocity and. the greatest reduction in coronary vascular resistance in anesthetize d, open-chest rabbits.