Ventilatory response to transient perfusion of carotid chemoreceptors

Abstract

Properties of carotid chemoreceptors were evaluated in anesthetized dogs by measuring transient change in breath-by-breath minute ventilation (Ve) produced by brief (15–60 sec) infusion into common carotid arteries of blood of known Po₂, Pco₂, and pH while stopping blood flow from below. Evidence is presented that the preparation permits studying behavior of carotid chemoreceptors alone, no response to infusion of hypercapnic blood occurring after carotid body denervation. The carotid bodies reacted to infusion of hypercapnic blood as promptly as to cyanide, and responded significantly to increments in Pco₂ of only 2 mm Hg. Ventilatory response curves to increments in Pco₂ were obtained. Approximate magnitude of carotid chemoreceptor drive was evaluated by infusion of hyperoxic, hypocapnic blood (Po₂ > 500, Pco₂ < 10 mm Hg) which did not reduce Ve during O₂ breathing, reduced it 24% during air breathing, and from 62 to 100% (apnea) during hypoxia.