The influence of barosensory vessel mechanics on the vascular sympathetic baroreflex: Insights into ageing and blood pressure homeostasis
Pugh, Christopher J. A.
American Physiological Society
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Changes in the arterial baroreflex arc contribute to elevated sympathetic outflow and altered reflex control of blood pressure with human ageing. Utilizing ultrasound and sympathetic microneurography (muscle sympathetic nerve activity; MSNA) we investigated the relationships between aortic and carotid artery wall tension (indices of baroreceptor activation) and the vascular sympathetic baroreflex operating point (OP; MSNA burst incidence) in healthy, normotensive young (n = 27, 23 ± 3 years) and middle-aged men (n = 22, 55 ± 4 years). In young men, the OP was positively related to the magnitude and rate of unloading and time spent unloaded in the aortic artery (r = 0.56, 0.65 and 0.51, P = 0.02, 0.003 and 0.03), but not related to the magnitude or rate of unloading or time spent unloaded in the carotid artery (r = -0.32, -0.07 and 0.06, P = 0.25, 0.81 and 0.85). In contrast, in middle-aged men, the OP was not related to either the magnitude or rate of unloading or time spent unloaded in the aortic (r = 0.22, 0.21 and 0.27, P = 0.41, 0.43 and 031) or carotid artery (r = 0.48, 0.28 and -0.01, P = 0.06, 0.25 and 0.98). In conclusion, in young men, aortic unloading mechanics may play a role in determining the vascular sympathetic baroreflex OP. In contrast, in middle-aged men, barosensory vessel unloading mechanics do not appear to determine the vascular sympathetic baroreflex OP, and therefore do not contribute to age-related arterial baroreflex resetting and increased resting MSNA. KEYWORDS: muscle sympathetic nerve activity; barosensory vessel unloading mechanics; healthy ageing; sympathetic nervous system; baroreflex Page Break NEW AND NOTEWORTHY We assessed the influence of barosensory vessel mechanics (magnitude and rate of unloading and time spent unloaded) as a surrogate for baroreceptor unloading. In young men, aortic unloading mechanics are important in regulating the operating point of the vascular sympathetic baroreflex, whereas in middle-aged men, these arterial mechanics do not influence this operating point. The age-related increase in resting muscle sympathetic nerve activity does not appear to be driven by altered baroreceptor input from stiffer barosensory vessels.
American Journal of Physiology - Heart and Circulatory Physiology;
Lord, R.N., Wakeham, D.J., Pugh, C.J., Simpson, L.L., Talbot, J.S., Lodge, F.M., Curry, B.A., Dawkins, T.G., Shave, R.E. and Moore, J.P., (2020) 'The influence of barosensory vessel mechanics on the vascular sympathetic baroreflex: insights into ageing and blood pressure homeostasis', American Journal of Physiology-Heart and Circulatory Physiology.
Article published in American Journal of Physiology - Heart and Circulatory Physiology on 10 July 2020, available at: https://doi.org/10.1152/ajpheart.00265.2020.
Cardiff Metropolitan University (Grant ID: Cardiff Metropolian (Internal))
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