Aortic body chemoreceptor responses to changes in PCO2 and PO2 in the cat.
Responses of aortic chemoreceptor afferents to a range of arterial carbon dioxide tension (Paco2) changes at various levels of arterial oxygen tension (Pao2) were investigated in 18 cats anesthetized with alpha-chloralose and maintained at 38 degrees C. Aortic chemoreceptor activity, end-tidal oxygen pressure, end-tidal carbon dioxide pressure, and arterial blood pressure were continuously monitored. Arterial blood gases were measured in steady states. Single or a few clearly identifiable afferents were studied during changes and steady states of Pao2 and Paco2. All the aortic chemoreceptor afferent discharge rates increased with Paco2 increases from hypercapnia (10-15 Torr) to normocapnia and moderate hypercapnia (30-50 Torr) and with Pao2 decreases from above 400 to 30 Torr. Hypoxia augmented the response to Paco2 most effectively in the range of 10-40 Torr. At any Pao2, the discharge rate reached a plateau with sufficient intensity of hypercapnia. The Paco2 stimulus threshold at a Pao2 of 440 Torr was about 15 Torr, and at a Pao2 of 60 Torr it was 10 Torr. In the transition from hypocapnia to hypercapnia, responses increased gradually, usually without an overshoot. The steady-state responses to Paco2 of the majority of aortic chemoreceptors resembled those of carotid chemoreceptors. The responses of both receptors can be attributed to the same basic type of mechanism.
D000818:Animals; D001016:Aortic Bodies / Q000502:physiology*; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood*; D002415:Cats; D002628:Chemoreceptor Cells / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010100:Oxygen / Q000097:blood*; D010234:Paraganglia, Nonchromaffin / Q000502:physiology*
D002245:Carbon Dioxide; D010100:Oxygen