Effects of Anoxia on the Vascular Resistance of the Dog's Hind Limb

Abstract

In anesthetized dogs, the inhalation of 5 per cent oxygen caused vasoconstriction of perfused hind limb but vasodilatation occurred during reoxygenation. The vasoconstriction during anoxia amounted to a mean increase of vascular resistance of +12 per cent if blood from the same anoxic dog was used for perfusion, and to +35 per cent if blood from a nonanoxic donor was used. This vasoconstrictor response was almost entirely the outcome of anoxemic stimulation of chemoreceptors in the carotid and aortic bodies. The vasodilatation during reoxygenation persisted after chemoreceptor denervation, but was eliminated by either spinal cord transection or denervation of the limb. The nervous pathways responsible for this postanoxic vasodilatation were resistant to bretylium but were partially blocked by either atropine or hexamethonium.