title: Role of the carotid body chemoreceptors in baroreflex control of blood pressure during hypoglycaemia in humans.
abstract: Activation of the carotid body chemoreceptors with hypoxia alters baroreceptor-mediated responses. We aimed to examine whether this relationship can be translated to other chemoreceptor stimuli (i.e. hypoglycaemia) by testing the following hypotheses: (i) activation of the carotid body chemoreceptors with hypoglycaemia would reduce spontaneous cardiac baroreflex sensitivity (sCBRS) in healthy humans; and (ii) desensitization of the carotid chemoreceptors with hyperoxia would restore sCBRS to baseline levels during hypoglycaemia. Ten young healthy adults completed two 180 min hyperinsulinaemic [2 mU (kg fat-free mass)(-1) min(-1)], hypoglycaemic (∼ 3.2 μmol ml(-1)) clamps, separated by at least 1 week and randomized to normoxia (arterial partial pressure of O2, 122 ± 10 mmHg) or hyperoxia (arterial partial pressure of O2, 424 ± 123 mmHg; to blunt activation of the carotid body glomus cells). Changes in heart rate, blood pressure, plasma catecholamines, heart rate variability (HRV) and sCBRS were assessed. During hypoglycaemia, HRV and sCBRS were reduced (P < 0.05) and the baroreflex working range was shifted to higher heart rates. When hyperoxia was superimposed on hypoglycaemia, there was a greater reduction in blood pressure and a blunted rise in heart rate when compared with normoxic conditions (P < 0.05); however, there was no detectable effect of hyperoxia on sCBRS or HRV during hypoglycaemia (P > 0.05). In summary, hypoglycaemia-mediated changes in HRV and sCBRS cannot be attributed exclusively to the carotid chemoreceptors; however, the chemoreceptors appear to play a role in resetting the baroreflex working range during hypoglycaemia.
authors.affiliation: * Department of Anesthesiology, Mayo Clinic, 200 1st Street SW, SMH Joseph 4-184, Rochester, MN 55905, USA.    joyner.michael@mayo.edu.
authors.forename: Jacqueline K
authors.initials: JK
authors.lastname: Limberg
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Taylor
authors.forename: Simmi
authors.initials: S
authors.lastname: Dube
authors.forename: Rita
authors.initials: R
authors.lastname: Basu
authors.forename: Ananda
authors.initials: A
authors.lastname: Basu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Joyner
authors.forename: Erica A
authors.initials: EA
authors.lastname: Wehrwein
mesh_terms: D000328:Adult; D017704:Baroreflex; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D002344:Carotid Body / Q000378:metabolism / Q000503:physiopathology*; D002395:Catecholamines / Q000097:blood; D005260:Female; D015309:Glucose Clamp Technique; D006339:Heart Rate; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology; D007003:Hypoglycemia / Q000097:blood / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D008297:Male; D012119:Respiration; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002395:Catecholamines; D007328:Insulin