Neural activity of the cardiac baroreflex decreases with age in normotensive and hypertensive subjects.
OBJECTIVE
Baroreflex control of the heart rate is impaired in hypertensive subjects and decreases with age. The decrease in cardiac baroreflex sensitivity (BRS) is often ascribed to decreased distension of the pressure-sensing arterial wall segments. However, alterations in the sensing and processing of neural signals may be involved as well.


METHODS
Conventionally, both vessel wall stiffness and the sensing and neural processing of the baroreflex are incorporated in the measure of pressure-derived BRS. We introduce stretch-derived BRS, which only considers the sensing and neural components of the baroreflex.


METHODS
To determine stretch-derived BRS in a non-invasive manner, we measured the spontaneously occurring low-frequency variations (range, 0.06-0.12 Hz) in the carotid artery diameter and the corresponding R-R interval fluctuations, and determined the associated transfer function. The stretch-derived BRS in a group of age-matched (age range, 25-72 years) normotensive (n = 20) and hypertensive (n = 21) subjects was compared.


RESULTS
In both subject groups the stretch-derived BRS decreased significantly with age. Moreover, the stretch-derived BRS of both groups was only different below 50 years of age.


CONCLUSIONS
The analysis of low-frequency fluctuations in the carotid artery diameter demonstrates that aging as well as hypertension are associated with impaired neural control of the baroreflex. Beyond 50 years of age the effect of hypertension cannot be distinguished from the effect of aging.
Kornet
Lilian
L
Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands.
Hoeks
Arnold Pg
AP
Janssen
Ben Ja
BJ
Houben
Alphons J
AJ
De Leeuw
Peter W
PW
Reneman
Robert S
RS
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001341:Autonomic Nervous System / Q000502:physiology; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002339:Carotid Arteries / Q000502:physiology; D005260:Female; D006321:Heart / Q000294:innervation / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged