effect of dopamine and blockade of dopaminergic and adrenergic receptors on coronary blood flow in ischemic rabbit myocardium the effect of a broad dose range of dopamine on coronary blood flow was studied in rabbits with coronary artery occlusion dopaminergic and adrenergic receptor blockade was established to distinguish the mechanism of the dopamineinduced increase in coronary blood flow dopamine 10 100 or 1000 microgramskgmin was infused in the presence of dopaminergic beta or alphaadrenergic receptor blockade coronary blood flow as measured by radiolabeled microspheres and hemodynamic parameters were monitored in 60 anesthetized openchest rabbits dopamine 1000 microgramskgmin significantly increased coronary blood flow 157 in normal and 118 in occluded rabbit myocardium propranolol 2 mgkg prevented the dopamineinduced increases in coronary blood flow within occluded and nonoccluded myocardium practolol 2 mgkg blunted the coronary blood flow increases within occluded myocardium but flow within normal myocardium remained significantly elevated in animals given phenoxybenzamine 2 mgkg dopamine infusion produced significant blood pressure reductions along with no change in either occluded or nonoccluded coronary blood flow bulbocapnine 8 mgkg a dopamine receptor antagonist did not block blood flow increases in normal myocardium but prevented significant increases in blood flow within occluded myocardium it can be concluded that direct or indirect vasodilator receptors dopaminergic beta 1 and beta 2adrenoceptors must be stimulated and perfusion pressure must not fall in order for dopamine to produce increases of coronary blood flow within occluded myocardium