Studies on peripheral circulation and epinephrine sensitization following sympathectomy

Abstract

Experiments on dogs were performed to study the effects of lumbar sympathectomy on the peripheral circulation of the hind limbs. Significant rises of distal cutaneous temperatures and arterial blood flow and a decrease of peripheral arterial pressure followed preganglionic denervation. Epinephrine was injected intravenously immediately after unilateral sympathectomy. An increase of peripheral arterial blood pressure and flow, of greater extent and duration than on the control side, was noted. Because of the disagreement that exists as to the time of onset of sensitization to epinephrine, further experiments were performed on dogs after unilateral lumbar sympathectomy. When the continuity of the femoral arteries was maintained, no difference in the effect of epinephrine on the peripheral arterial pressures of the limbs could be demonstrated, but a difference was very evident when the peripheral arterial beds were isolated. In control animals, administration of epinephrine resulted in a brief rise of pressure and outflow in the femoral veins, coincident with the first part of the rise of arterial pressure. The pressures and flow then abruptly decreased to the control level, or less, during the latter portion of the arterial response. This also occurred after sympathectomy, but was less marked on the denervated side. Finally, plethysmographic studies were carried out on an intact and on a denervated kidney. Epinephrine given immediately after the postganglionic denervation similarly resulted in a greater decrease of volume and a longer duration of the effect in the denervated organ. These data suggest strongly that hypersensitivity of blood vessels to epinephrine may occur immediately after both preganglionic and postganglionic sympathectomy.