title: Baroreflex buffering is reduced with age in healthy men.
abstract: BACKGROUND
  Baroreflex buffering is an important mechanism in arterial blood pressure control. The effect of healthy (physiological) aging on tonic baroreflex buffering in humans is unknown.
  
  
  RESULTS
  Baroreflex buffering was determined in 27 young (aged 25+/-1 years) and 16 older (aged 65+/-1 years) healthy normotensive men by measuring the potentiation of the systolic blood pressure (SBP) responses to a phenylephrine bolus (BRBbolus) and incremental infusion (BRBslope) during compared with before ganglionic blockade with trimethaphan. The SBP responses to phenylephrine either were not different or greater in the older men before ganglionic blockade, but smaller during ganglionic blockade. BRBbolus (2.1+/-0.4 versus 5.1+/-0.7, P<0.001) and BRBslope (1.6+/-0.2 versus 3.5+/-0.4, P<0.0001) were approximately 115% smaller in the older men. Baroreflex buffering was not consistently related to mean levels or variability of blood pressure or heart rate, or to cardiovagal baroreflex sensitivity, but correlated with muscle sympathetic nerve activity (BRBbolus: r=-0.55, BRBslope: r=-0.69, P<0.005) and the SBP responses to phenylephrine during ganglionic blockade (BRBbolus: r=0.53; BRBslope: r=0.98, P<0.0001). BRBbolus was also inversely related to the SBP response to phenylephrine before ganglionic blockade (r=-0.78, P<0.0001).
  
  
  CONCLUSIONS
  Physiological aging in men is associated with a marked reduction in baroreflex buffering. The decrease in baroreflex buffering with aging is related to increases in basal sympathetic nerve activity and reductions in systemic alpha1-adrenergic vascular responsiveness. These findings are helpful for interpreting changes in baroreflex buffering in older patients with cardiovascular disease, as well as changes in responsiveness to vasoactive drugs with aging.
authors.affiliation: Department of Kinesiology and Applied Physiology, University of Colorado at Boulder, UCB 354, Boulder, CO 80309, USA. pamela@spot.colorado.edu
authors.forename: Pamela Parker
authors.initials: PP
authors.lastname: Jones
authors.forename: Demetra D
authors.initials: DD
authors.lastname: Christou
authors.forename: Jens
authors.initials: J
authors.lastname: Jordan
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Seals
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D001341:Autonomic Nervous System / Q000502:physiology; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002320:Cardiovascular Physiological Phenomena; D005730:Ganglionic Blockers / Q000494:pharmacology; D006339:Heart Rate; D006801:Humans; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000502:physiology; D014294:Trimethaphan / Q000494:pharmacology
chemical_list: D005730:Ganglionic Blockers; D010656:Phenylephrine; D014294:Trimethaphan