Specificity of H ion concentration as a carotid chemoreceptor stimulus

Abstract

The present study was designed to separate quantitatively the relative contributions of (H+) and Pco₂ as chemoreceptor stimuli. The integrated electrical activity from the entire Hering's nerve of the cat was measured and correlated with values of (H⁺), Pco₂, and Po₂ of arterial blood. By utilizing a combination of respiratory and metabolic acidosis or alkalosis, the effect of (H⁺) on carotid body nerve activity could be separated from that of Pco₂. Most studies were performed at high Po₂, a few against a changing hypoxic background. The results indicate: 1) the pre-eminence of (H⁺) as a chemoreceptor stimulus, CO₂ acting only by virtue of its effect in altering (H⁺); 2) the relationship between (H⁺) or Pco₂ and chemoreceptor activity is nonlinear; 3) the potentiation between hypoxia and hypercapnia at the chemoreceptor level is due primarily to interaction between low oxygen tension and increased (H⁺), independent of Pco₂. The significance of these findings to the exchange of CO₂ and of (H⁺) and (HCO3^-) ions between the intracellular and extracellular milieu of the carotid chemoreceptor cells is discussed. Submitted on September 28, 1962