Catecholamine-induced redistribution of blood flow in the unanesthetized rat

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Abstract
The effects of eplnephrine and norepinephrine infusion of 0.5 and 5.0 /xg/kg per min on the distribution of blood through 15 organs and on the cardiac output have been measured in unanesthetized, unrestrained rats. The lower epinephrine dose increased cardiac output by 43%. Cardiac output was shifted significantly to the kidney and away from the adrenal, thyroid, spleen, and skin, although net perfusion decreased to no organ. Partly as a result of the increased cardiac output, the net flow of blood increased to the posterior pituitary, adrenal, pineal body, heart, kidney, lung, gut, liver, and carcass. Cardiac output at the higher dose remained unchanged, due to increased peripheral resistance, and was redistributed to the kidney, pineal body, and liver, and away from the carcass, skin, spleen, and thyroid; net flow of blood to most organs paralleled the fractional distribution. Norepinephrine at the lower dose did not change the cardiac output; net blood flow increased significantly to one organ only-the thyroid. At the high dose, the cardiac output fell by 30% and was redistributed to both parts of the pituitary, the pineal body, heart, lung, and gut, and away from the skin and carcass. The net blood flow increased only to the pineal body and lung and decreased markedly to the skin and carcass. The data strongly suggest that epinephrine is capable of organizing patterns of blood flow under physiological conditions.