Pressor Response to Adrenalin Shown by Spinal Dogs

¹ From the Department of Physiology, College of Physicians and Surgeons, New York City

Intravenous injection of Adrenalin (1 ml of 1:300,000–1:25,000) into 10 normal, anesthetized (Nembutal) dogs produced an average increase in mean arterial pressure which amounted to about 25 at the lower and 100 mm Hg at the higher doses. Essentially the same responses were shown by seven anesthetized, vagotomized dogs and five anesthetized, vagotomized animals in which the carotid regions were denervated. Eight anesthetized dogs with spinal cords cut between C8 and T1 showed after Adrenalin injection an average percentage increase in mean arterial pressure which was some threefold greater than that found in normal, anesthetized animals. This difference was increased still further by bilateral section of the vagi in eight spinal dogs. Section of the spinal cord one or two segments below C8 to T1 (4 dogs) decreased the response to Adrenalin. The increase in mean arterial pressure induced by the intravenous injection of Adrenalin was greater in six spinal dogs (C8 to T1) anesthetized with Nembutal than in two similar unanesthetized animals. Acute changes in plasma volume did not influence the magnitude of the blood pressure response to Adrenalin shown by four high spinal animals.