Responses of aortic chemoreceptors.

Abstract

In cats anesthetized with chloralose impulses from single chemoreceptor fibers in the vagus or aortic nerve was recorded. These fibers were identified as chemoreceptors by their increased discharge of irregular impulses during asphyxia. The anatomical location of the chemosensitive endings was identified by the latency of the increased firing after injection of nicotine into the right atrium or the root of the aorta. All fibers in the vagi of 5 cats were examined for chemoreceptor activity. The 48 fibers studied all arose in the systemic arterial circulation. None was localized in the right heart or pulmonary artery. Conduction velocities (35 fibers) ranged from 0.9 to 10 m/sec. The maximal frequency of discharge during hypoxia (12 fibers) was 8-12 impulses/sec. The threshold of stimulation, in terms of inspired PO2, was 80-160 mm Hg. The effect of hypercapnia upon the rate of firing during hypoxia was variable and small.