The Coronary Blood Flow Effects Caused by the Carotid Sinus Reflex and the Exogenous Catecholamine

It is well known that the carotid sinus reflex affects the blood flow in the coronary artery. Previous studies from this laboratory have indicated that the catecholamine in the canine blood increased during both common carotid arteries occlusion.The present experiment employed 18 mongrel dogs (weighing 10 to 20Kg) which were investigated by the open chest method after being anesthetized with the sodium pentobarbital.The cardiac output, the blood flow in the descending branch of the left coronary artery, and the femoral artery pressure were all simulatneously measured with the electromagnetic flow meter and the electromagnetic transducer. These machines recorded blood pressure, coronary blood flow and cardiac output before and during the stimulations caused by the carotid occlusion or the exogenous catecholamine infusion. Both the occlusion and the infusion were investigated under 3 conditions (with nonadrenergic blockade, with an alphareceptor blockade, and with a beta-receptor blockade). Bilaterally, the common carotid occlusion revealed a noticeable increase of the coronary blood flow and the blood pressure without any increased cardiac output.The alpha-receptor blockade inhibited the change caused by the common carotid occlusion but the beta-receptor blockade did not. This study suggests that the increased blood pressure and the alpha-adrenergic receptor during the common carotid arteries occlusion play a part in an increase of the coronary blood flow.