caa a22 4500 463157834 CHVBK 20180406164739.0 cr unu---uuuuu 170326e20070201xx s 000 0 eng 10.1007/s10286-006-0390-z doi (NATIONALLICENCE)springer-10.1007/s10286-006-0390-z Daytime variability in carotid baroreflex function in healthy human subjects [Elektronische Daten] [Victoria Cooper, Mark Elliott, Stan Pearson, Claire Taylor, Roger Hainsworth] Variability of blood pressure is limited by arterial baroreceptors, yet blood pressure still shows circadian changes. This study was undertaken to examine if the responses to the carotid baroreflex also change throughout the day. Responses of cardiac interval (RR), mean arterial pressure (MAP) and vascular resistance (VR) to carotid baroreflex stimulation and inhibition using pressures and suction applied to a neck chamber, were measured in 14 healthy, normotensive subjects. Studies were carried out at three hourly intervals between 09:00 and 21:00hours. Stimulus-response curves were defined and the first differential of the curve was calculated to establish reflex sensitivity (maximal slope) and "operating” point (estimated carotid sinus pressure at point of maximum slope, OP). The principal findings are: (1) baroreflex sensitivity for the control of VR was at its highest at 09:00 (−3.4±0.6units) compared to 12:00 (−1.9±0.4units), 15:00 (−2.0±0.4units) and 18:00 (−1.9±0.3units) (all P<0.05); (2) baroreflex OP for the control of MAP was at its lowest at 09:00 (P<0.01); (3) baroreflex sensitivity for control of VR was significantly correlated with prevailing mean pressure (P<0.05) and OP for the control of MAP (P<0.02); (4) OP for control of RR, MAP and VR are all highly correlated to prevailing MAP (P<0.0001). Our results suggest that baroreflex function varies throughout the day and this favors higher sensitivity and lower blood pressure in the mornings. We speculate that this may be of importance in long-term blood pressure regulation. Steinkopff Verlag Darmstadt, 2007 carotid baroreceptor reflex nationallicence vascular resistance nationallicence blood pressure nationallicence Cooper Victoria Institute for Cardiovascular Research, University of Leeds, LS2 9JT, Leeds, UK aut Elliott Mark Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut Pearson Stan Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut Taylor Claire Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut Hainsworth Roger Institute for Cardiovascular Research, University of Leeds, LS2 9JT, Leeds, UK aut Clinical Autonomic Research Steinkopff-Verlag; www.steinkopff.springer.de 17/1(2007-02-01), 26-32 0959-9851 17:1<26 2007 17 10286 https://doi.org/10.1007/s10286-006-0390-z text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10286-006-0390-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Cooper Victoria Institute for Cardiovascular Research, University of Leeds, LS2 9JT, Leeds, UK aut NATIONALLICENCE 700 1- Elliott Mark Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut NATIONALLICENCE 700 1- Pearson Stan Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut NATIONALLICENCE 700 1- Taylor Claire Dept. of Respiratory Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK aut NATIONALLICENCE 700 1- Hainsworth Roger Institute for Cardiovascular Research, University of Leeds, LS2 9JT, Leeds, UK aut NATIONALLICENCE 773 0- Clinical Autonomic Research Steinkopff-Verlag; www.steinkopff.springer.de 17/1(2007-02-01), 26-32 0959-9851 17:1<26 2007 17 10286 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer