Baroreflex Buffering Is Reduced With Age in Healthy Men

Jones, P. P.; Christou, Demetra D.; Jordan, Jens; Seals, Douglas R.

doi:10.1161/01.cir.0000057811.86187.88

Cited by 126 publications

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“…The ability of baroreflexes to "buffer" acute changes in BP under such conditions (ie, baroreflex buffering [BRB]) is reduced in certain physiological 9 and disease 10 states associated with impaired short-term BP regulation and/or altered responsiveness to vasoactive medications. In light of previous reports of less effective short-term regulation of BP in women than in men, 1,2,6,[11][12][13][14] we also hypothesized that premenopausal women have lower BRB of BP than men of similar age.…”

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Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

et al. 2005

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“…We also measured resting sympathoadrenal activity and systemic ␣ 1 -adrenergic vascular responsiveness, 2 key determinants of these expressions of ANS control of BP, 7,9,10,15,16 to determine their potential mechanistic roles in any gender-related differences observed.…”

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Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

et al. 2005

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“…Renal sympathetic nerve activity also has been reported to increase, but there is impaired baroreflex control of both heart rate and blood pressure (Hajduczok et al 1991). In human males, a marked decline in baroreflex buffering of blood pressure is due to, at least in part, a marked reduction in a-adrenergic receptor function (Castellani et al 1999;Jones et al 2003). Speculation on how these findings could be reconciled might include: 1) a comparison of prazosin binding in the rat parotid cell indicating a naturally occurring post-a-adrenergic receptor defect in signal transduction (Ishikawa et al 1989); 2) Age-related impairments in a-adrenergic responsiveness could be partially caused by alterations in the coupling of a-adrenergic receptors and G-proteins (Myamoto et al 1992); 3) A decline in the G protein amplification of constriction (Robert et al 1998) and 4) Competitive binding experiments (prazosin) revealed that maximal binding of the a-adrenergic receptor of the interlobar arteries is reduced 25% by 10 months of age and 50% by 18 months of age (Passmore et al 2005).…”

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Decreased alpha-adrenergic constriction of renal preglomerular arteries occurs with age and is gender-specific in the rat

Falcone

Joshua

Passmore

2005

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Age and/or gender appear to moderate alpha-adrenergic mediated constrictor mechanisms found in the interlobar arteries of the Munich Wistar rat. We have determined the extent of constriction to alpha-adrenergic receptor stimulation using norepinephrine, phenylephrine and A61603 (a 1A -adrenergic receptor agonist) as a function of age and gender. Norepinephrine produced less constriction in male-derived arteries at ages greater than eight months as compared to the younger adult male (four to six months). The arteries derived from females did not demonstrate altered constriction until greater than 15 months of age. Similarly, arteries derived from the male demonstrated weaker constrictions to phenylephrine (10 j6 to 10 j3 M) at ages greater than eight months while arteries from females showed differences at greater than 15 months. In contrast, the effective concentration of norepinephrine to cause a 50% maximal constriction (EC 50 ) was significantly less in the four to five-month-old male rats compared to the pooled data from older groups. Interestingly, four to five month old males had A61603 EC 50 values similar to the 8-to 12-month and 15+ old females. These studies conclude that an age related loss of sympathetic a-adrenergic constriction of renal interlobar arteries is present in Munich Wistar rats. Furthermore, this loss, while similar along longitudinal aspects of age, is also different as a function of gender with the loss of a-adrenergic constrictor function delayed in the female when compared to the male.

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“…For example, respiration makes blood pressure fluctuate with every breath (13), while physical or mental stress elevates blood pressure for minutes or even longer. The arterial baroreflex is a negativefeedback mechanism that effectively buffers such incidental blood pressure fluctuations (11,20,21,23). In negativefeedback systems, feedback delay often causes resonance in a given frequency band; this is the price to be paid for effective buffering at other frequencies.…”

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Baroreflex sensitivity, blood pressure buffering, and resonance: what are the links? Computer simulation of healthy subjects and heart failure patients

Vooren

Gademan²,

Swenne

et al. 2007

Journal of Applied Physiology

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Van de Vooren H, Gademan MG, Swenne CA, TenVoorde BJ, Schalij MJ, Van der Wall EE. Baroreflex sensitivity, blood pressure buffering, and resonance: what are the links? Computer simulation of healthy subjects and heart failure patients. J Appl Physiol 102: 1348 -1356, 2007. First published December 21, 2006; doi:10.1152/japplphysiol.00158.2006.-The arterial baroreflex buffers slow (Ͻ0.05 Hz) blood pressure (BP) fluctuations, mainly by controlling peripheral resistance. Baroreflex sensitivity (BRS), an important characteristic of baroreflex control, is often noninvasively assessed by relating heart rate (HR) fluctuations to BP fluctuations; more specifically, spectral BRS assessment techniques focus on the BP-to-HR transfer function around 0.1 Hz. Skepticism about the relevance of BRS to characterize baroreflex-mediated BP buffering is based on two considerations: 1) baroreflex-modulated peripheral vasomotor function is not necessarily related to baroreflex-HR transfer; and 2) although BP fluctuations around 0.1 Hz (Mayer waves) might be related to baroreflex BP buffering, they are merely a not-intended side effect of a closed-loop control system. To further investigate the relationship between BRS and baroreflex-mediated BP buffering, we set up a computer model of baroreflex BP control to simulate normal subjects and heart failure patients. Output variables for various randomly chosen combinations of feedback gains in the baroreflex arms were BP resonance, BP-buffering capacity, and BRS. Our results show that BP buffering and BP resonance are related expressions of baroreflex BP control and depend strongly on the sympathetic gain to the peripheral resistance. BRS is almost uniquely determined by the vagal baroreflex gain to the sinus node. In conclusion, BP buffering and BRS are unrelated unless coupled gains in all baroreflex limbs are assumed. Hence, the clinical benefit of a high BRS is most likely to be attributed to vagal effects on the heart instead of to effective BP buffering. autonomic nervous system; cardiovascular variability; Mayer waves; spectral analysis; transfer function IN DAILY LIFE, multiple processes perturb blood pressure. The duration of these challenges varies widely. For example, respiration makes blood pressure fluctuate with every breath (13), while physical or mental stress elevates blood pressure for minutes or even longer. The arterial baroreflex is a negativefeedback mechanism that effectively buffers such incidental blood pressure fluctuations (11,20,21,23). In negativefeedback systems, feedback delay often causes resonance in a given frequency band; this is the price to be paid for effective buffering at other frequencies. Resonance in blood pressure (5,8,12,31,49) manifests in the form of the well-known Mayer (22, 33) waves (beat-to-beat blood pressure oscillations with a frequency of ϳ0.1 Hz/period of ϳ10 s). Effective baroreflex blood pressure buffering occurs below the Mayer frequency (10, 16).Besides a sympathetic limb that modulates peripheral resistance, the baroreflex has ...

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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. Methods and Results-Baroreflex

Cited by 126 publications

References 34 publications

Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

Decreased alpha-adrenergic constriction of renal preglomerular arteries occurs with age and is gender-specific in the rat

Baroreflex sensitivity, blood pressure buffering, and resonance: what are the links? Computer simulation of healthy subjects and heart failure patients

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