The Influence of Respiratory Gas Mixtures on Arterial Pressure and Vascular Reactivity in "Normal" and Hypertensive Dogs

Abstract

The reactivity of the vascular tree to chemical stimuli is of fundamental importance in both hypertension and shock. Refractoriness and hypotension can be elicited by stimuli arising in the sympathetic ganglions as a result of their stimulation by carbon dioxide. "Total" autonomic ganglionectomy thus prevents the appearance of refractoriness and aids in production of the supernormal hypotensive response to carbon dioxide. Dogs with renal experimental hypertension differ from those with neurogenic hypertension in that they react normally to carbon dioxide and several other vasoactive substances. The neurogenic hypertensives exhibit greatly heightened depressor responses and hence vasomotor activity. The mechanism for refractoriness is intact in both groups of animals and does not appear overactive in either. The neurogenic mechanism for the production of refractoriness is lost in the sympathectomized animal.