Neural Mechanisms
The last four decades of extensive investigations have revealed that sympathetic nervous system plays a critical pathogenic role in blood pressure elevation and sustained hypertension. The regional noradrenaline spillover technique was a major breakthroug
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Neural Mechanisms Dagmara Hering, Gino Seravalle, Guido Grassi, and Krzysztof Narkiewicz
5.1
ympathetic Nervous System Activation in Human S Hypertension
It is not clear whether the hemodynamic characteristics of the initial phase of primary hypertension are induced by increased peripheral resistance or raised cardiac output [1]. Approximately one third of younger adults with borderline and/or mild hypertension present with hyperkinetic hypertension with increased heart rate, cardiac output, forearm blood flow and plasma noradrenaline (NA) levels [2]. Other abnormalities also commonly characterize the hyperkinetic state including increased renal blood flow and plasma renin activity [3]. The
D. Hering (*) Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland Baker IDI Heart and Diabetes Institute, Melbourne, VIC, Australia e-mail: [email protected] G. Seravalle Istituto Auxologico Italiano IRCCS Ospedale San Luca, Milan, Italy G. Grassi Clinica Medica, Department of Medicine and Surgery, University Milano-Bicocca, Milan, Italy IRCCS Multimedica, Sesto San Giovanni, Milan, Italy e-mail: [email protected] K. Narkiewicz Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland e-mail: [email protected] © Springer Nature Switzerland AG 2019 M. Dorobantu et al. (eds.), Hypertension and Heart Failure, Updates in Hypertension and Cardiovascular Protection, https://doi.org/10.1007/978-3-319-93320-7_5
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hyperkinetic state is likely to indicate increased sympathetic activity. The activation of the sympathetic nervous system (SNS) in human hypertension has been convincingly demonstrated through the use of two state-of-the-art methods, namely, the isotope dilution method for quantifying NA spillover rates and the postganglionic efferent sympathetic nerve recording with microneurography technique. NA is the main neurotransmitter of sympathetic nerves, and the rate of its release from nerve terminals allows for the measurement of sympathetic nerve activity. Quantifying NA kinetics with spillover technique was a major breakthrough in studies on the sympathetic nervous system. Although the overall (total body) NA spillover in hypertension is moderate, a selectively augmented sympathetic outflow from the heart and the kidney characterizes primary hypertension, likely contributing to established hypertension [4, 5]. Augmented NA from the renal sympathetic nerves is evident in untreated patients with essential hypertension (EH), mostly adults below the age of 40, and is a prime mover for blood pressure (BP) rise [4, 6]. Increased cardiac NA spillover and decreased NA neuronal reuptake further potentiate sympathetic activation in maintaining elevated BP [7]. In comparison to younger hypertensives, NA release from sympathetic nerves has been found to be lower as a result of an age-dependent fall in NA plasma clearance in essential hypertension [8]. With ageing and disease progression, cardiac output generally becomes normal in unco
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