Browsing by Subject "ABP"
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Item Peripheral and Central Muscarinic Cholinergic Receptors in Arterial Blood Pressure Regulation(1999-12-01) Wray, David Walter; Shi, Xiangrong; Gwirtz, Patricia A.; Raven, Peter B.Wray, David Walter, Peripheral and Central Muscarinic Cholinergic Receptors in Arterial Blood Pressure Regulation. Master of Science (Biomedical Sciences), December, 1999, 70 pp., 7 tables, 8 illustrations, references, 83 titles. This study was designed to test the hypothesis that an age-related vagal dysfunction compromises arterial blood pressure (ABP) regulation. Changes in heart rate (HR) and ABP during lower body negative pressure (LBNP) were compared between ten elderly (≥60 yrs) and ten young (≤30 yrs) adults. A separate, young group (n=10) was also assessed following muscarinic cholinergic (MC) blockade with atropine (central and peripheral receptor blockade) or glycopyrrolate (peripheral receptor blockade) to simulate vagal dysfunction. During the onset of LBNP -40 too, orthostatic hypotension (OH) was observed in both the older subjects and the post-blockade younger subjects, with a diminished HR response. Furthermore, the reflex response to hypertensive stimuli was augmented in the post-blockade younger subjects, also associated with a diminution in HR response. We concluded that age-related or pharmacologically stimulated vagal dysfunction compromises ABP regulation during hypotensive and hypertensive stimuli, and that the difference between atropine and glycopyrrolate was insignificant.Item Sympathetic Cardiac Influence and Arterial Blood Pressure Instability(2002-09-01) Formes, Kevin John; Shi, Xiangrong; Downey, H. Fred; Gwirtz, Patricia A.Formes, Kevin John, Sympathetic Cardiac Influence and Arterial Blood Pressure Instability. Master of Science (Biomedical Sciences) September 2002, 51 pp., 3 tables, 5 illustrations, 36 references. This study was designed to determine the role of β1-adrenoreceptors in arterial blood pressure (ABP) regulation during an orthostatic challenge. Metoprolol was used to block β1-adrenoreceptors. Atropine, a peripheral and central acting muscarinic blocker, was used to inhibit vagal influences on heart rate. Lower body negative pressure (LBNP) was used to stimulate an orthostatic hypotensive stimulus before and after receptor blockade. Metoprolol administration significantly increased baroreflex sensitivity (BRS) and significantly decreased the reflex increase baroreflex sensitivity (BRS) and significantly decreased the reflex increase in plasma renin activity (PRA) in response to a hypotensive stimulus. Therefore we suggest that the attenuation of PRA is counterbalanced by an increased heart rate reserve, which allows the heart rate to increase more in response to decreases in venous return. This increase in cardiac responsiveness was abolished with the administration of atropine. Therefore, we conclude that acute administration of metoprolol causes (i) improved ABP stability, as indicated by a diminished augmentation of low frequency (LF) ABP variability and (ii) attenuates the increase in PRA during LBNP induced central hypovolemic challenge.