Aldosterone blunts the baroreflex response in man

1998 ◽  
Vol 95 (6) ◽  
pp. 687-692 ◽  
Author(s):  
K. M. YEE ◽  
A. D. STRUTHERS
Keyword(s):  
Blood Pressure ◽  
Animal Models ◽  
Sodium Nitroprusside ◽  
Baroreflex Sensitivity ◽  
Crossover Fashion ◽  
Healthy Male ◽  
Double Blind ◽  
Resting Blood Pressure ◽  
Blood Pressure Responses

1. Recent animal evidence suggests that aldosterone, like angiotensin II, may possess detrimental autonomic modulating properties. Aldosterone has been shown to impair the baroreflex response in animal models. This study is designed to test the hypothesis that aldosterone directly attenuates the baroreflex in vivo in man. 2. Fourteen healthy male volunteers [mean age (S.D.) 25 (9) years] received intravenous d-aldosterone (12 pmol·min-1·kg-1) and 5% dextrose (vehicle) in a double-blind crossover fashion, co-infused with incremental doses of intravenous phenylephrine and sodium nitroprusside. Aldosterone had no significant effect on resting blood pressure, heart rate or baroreflex response to sodium nitroprusside. However, reflex responses to phenylephrine were impaired with aldosterone (P< 0.01) while blood pressure responses were unaltered. Baroreflex sensitivity was significantly blunted in the aldosterone group [8.36±2.19 versus 10.12±2.27 ms/mmHg; P< 0.04]. 3. This study confirms previous observations from animal models that aldosterone impairs the baroreflex response. High aldosterone levels may contribute to the baroreflex dysfunction in cardiovascular diseases such as hypertension and heart failure.

Ascorbic acid increases cardiovagal baroreflex sensitivity in healthy older men

2004 ◽  
Vol 286 (6) ◽  
pp. H2113-H2117 ◽  
Author(s):  
Kevin D. Monahan ◽  
Iratxe Eskurza ◽  
Douglas R. Seals
Keyword(s):  
Oxidative Stress ◽  
Blood Pressure ◽  
Ascorbic Acid ◽  
Systolic Blood Pressure ◽  
Sodium Nitroprusside ◽  
Baroreflex Sensitivity ◽  
Older Men ◽  
Acid Infusion ◽  
Healthy Men ◽  
Phenylephrine Hydrochloride

Cardiovagal baroreflex sensitivity (BRS) declines with advancing age in healthy men. We tested the hypothesis that oxidative stress contributes mechanistically to this age-associated reduction. Eight young (23 ± 1 yrs, means ± SE) and seven older (63 ± 3) healthy men were studied. Cardiovagal BRS was assessed using the modified Oxford technique (bolus infusion of 50–100 μg sodium nitroprusside, followed 60 s later by a 100- to 150-μg bolus of phenylephrine hydrochloride) in triplicate at baseline and during acute intravenous ascorbic acid infusion. At baseline, cardiovagal BRS (slope of the linear portion of the R-R interval-systolic blood pressure relation during pharmacological changes in arterial blood pressure) was 56% lower ( P < 0.01) in older (8.3 ± 1.6 ms/mmHg) compared with young (19.0 ± 3.1 ms/mmHg) men. Ascorbic acid infusion increased plasma concentrations similarly in young (62 ± 9 vs. 1,249 ± 72 μmol/l for baseline and during ascorbic acid; P < 0.05) and older men (62 ± 4 vs. 1,022 ± 55 μmol/l; P < 0.05) without affecting baseline blood pressure, heart rate, carotid artery compliance, or the magnitude of change in systolic blood pressure in response to bolus sodium nitroprusside and phenylephrine hydrochloride infusion. Ascorbic acid (vitamin C) infusion increased cardiovagal BRS in older (Δ58 ± 16%; P < 0.01), but not younger (Δ − 4 ± 4%) men. These data provide experimental support for the concept that oxidative stress contributes mechanistically to age-associated reductions in cardiovagal BRS in healthy men.

scholarly journals Human neuropeptide Y potentiates α1-adrenergic blood pressure responses in vivo

1998 ◽  
Vol 275 (3) ◽  
pp. H760-H766 ◽  
Author(s):  
Leander V. Schuerch ◽  
Lilly M. Linder ◽  
Eric Grouzmann ◽  
Walter E. Haefeli
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Neuropeptide Y ◽  
Blood Pressure Response ◽  
Human Hand ◽  
Response Curves ◽  
Fourfold Increase ◽  
Dose Rates ◽  
Blood Pressure Responses

Human neuropeptide Y (hNPY) potentiates the postjunctional vasoconstrictor effects of α1-adrenoceptor agonists in animals and in human hand veins in vivo. We therefore hypothesized that such an interaction might also occur in the human arterial bed. With the present single-blind cross-over study in 12 healthy volunteers, the effect of subpressor doses of hNPY on the blood pressure response to α1-adrenoceptor stimulation was evaluated. Dose-response curves were constructed to intravenously infuse phenylephrine with and without coinfusion with two different doses of hNPY (1.4 and 14.3 pmol ⋅ kg−1 ⋅ min−1). Blood pressure, heart rate, and forearm blood flow were recorded, and plasma hNPY was determined. During infusion of the higher hNPY dose, which increased hNPY from 24.0 ± 12.0 to 495.1 ± 12.6 pmol/l, blood pressure curves were 2.4-fold shifted toward lower phenylephrine dose rates ( P < 0.001). Forearm vascular resistance showed a similar trend, whereas the counterregulatory decrease of heart rate was similar in both groups. In contrast, the lower hNPY dose rate producing a fourfold increase in hNPY concentrations did not modify the response to phenylephrine. This in vivo study in humans demonstrates that hNPY induced potentiating effects on α1-adrenergic constriction also in the systemic arterial circulation and suggests that circulating hNPY may participate in the control of vascular tone.

scholarly journals Sex differences in blood pressure control during 6° head-down tilt bed rest

2013 ◽  
Vol 304 (8) ◽  
pp. H1114-H1123 ◽  
Author(s):  
Natalia M. Arzeno ◽  
Michael B. Stenger ◽  
Stuart M. C. Lee ◽  
Robert Ploutz-Snyder ◽  
Steven H. Platts
Keyword(s):  
Blood Pressure ◽  
Sex Differences ◽  
Sodium Nitroprusside ◽  
Blood Pressure Control ◽  
High Frequency ◽  
Baroreflex Sensitivity ◽  
Orthostatic Intolerance ◽  
Bed Rest ◽  
Pressure Control ◽  
Sinus Arrhythmia

Spaceflight-induced orthostatic intolerance has been studied for decades. Although ∼22% of the astronaut corps are women, most mechanistic studies use mostly male subjects, despite known sex differences in autonomic control and postflight orthostatic intolerance. We studied adrenergic, baroreflex, and autonomic indexes during continuous infusions of vasoactive drugs in men and women during a 60-day head-down bed rest. Volunteers were tested before bed rest (20 men and 10 women) and around day 30 (20 men and 10 women) and day 60 (16 men and 8 women) of bed rest. Three increasing doses of phenylephrine (PE) and sodium nitroprusside were infused for 10 min after an infusion of normal saline. A 20-min rest period separated the phenylephrine and sodium nitroprusside infusions. Autonomic activity was approximated by spectral indexes of heart rate and blood pressure variability, and baroreflex sensitivity was measured by the spontaneous baroreflex slope. Parasympathetic modulation and baroreflex sensitivity decreased with bed rest, with women experiencing a larger decrease in baroreflex sensitivity by day 30 than men. The sympathetic activation of men and parasympathetic responsiveness of women in blood pressure control during physiological stress were preserved throughout bed rest. During PE infusions, women experienced saturation of the R-R interval at high frequency, whereas men did not, revealing a sex difference in the parabolic relationship between high-frequency R-R interval, a measurement of respiratory sinus arrhythmia, and R-R interval. These sex differences in blood pressure control during simulated microgravity reveal the need to study sex differences in long-duration spaceflight to ensure the health and safety of the entire astronaut corps.

Blood pressure variability and baroreflex sensitivity of a healthy male during cold pressor test that induced development of neurocardiogenic syncope

2016 ◽  
Vol 0 (0) ◽  
Author(s):  
Biswajit Sinha ◽  
Dinesh K. Dubey
Keyword(s):  
Blood Pressure ◽  
Baroreflex Sensitivity ◽  
Cold Pressor Test ◽  
Cold Pressor ◽  
Initial Increase ◽  
Healthy Male ◽  
Neurocardiogenic Syncope ◽  
Pressor Test ◽  
Present Case Study

AbstractThe cold pressor test (CPT) is a recognized physiological technique to evaluate autonomic cardiovascular function. The present case study assessed the cardiovascular response of a healthy adult male during 3 min of CPT.Heart rate (HR) by single-lead electrocardiography and blood pressure (BP) by an arterial tonometer of the participant on a beat-to-beat basis were recorded before and during CPT.HR during CPT showed a biphasic pattern with an initial increase from baseline (86 bpm) to the first 30 s of CPT (93 bpm) followed by a decrease. It dropped to 51 bpm during the last 30 s of CPT. Systolic blood pressure (SBP) increased from baseline (110 mmHg) to 1 min (122 mmHg) followed by a decrease. SBP immediately after CPT reduced to 57 mmHg. Diastolic blood pressure (DBP) from baseline (71 mmHg) slightly increased to 75 mmHg up to 90 s of the test, thereafter it registered a fall, and during the last 30 s of CPT, DBP fell to 30 mmHg. Stroke volume increased from baseline (75 mL/min) to the first 30 s (99 mL/min), followed by a slight reduction which was maintained till last of the test (70 mL/min). Cardiac output after an initial increase from baseline (6.4 L/min) to the first 30 s (9.2 L/min) decreased to 4.1 L/min during the last 30 s of the test. Baroreflex sensitivity (BRS) from baseline (9.32 ms/mmHg) plummeted to 6.67 ms/mmHg during the first 30 s of CPT followed by an increase, and after CPT, BRS was increased to 15.23 ms/mmHg. Other cardiovascular parameters such as myocardial contractility (dThe present case study described the modulation of cardiovascular functions of a healthy male during CPT, which finally led to the development of neurocardiogenic syncope characterized by hypotension and bradycardia.

Effects of angiotensin II (AT1) receptor blockade on cardiac vagal control in heart failure

2001 ◽  
Vol 101 (6) ◽  
pp. 559-566 ◽  
Author(s):  
J. C. VAILE ◽  
S. CHOWDHARY ◽  
F. OSMAN ◽  
H. F. ROSS ◽  
J. FLETCHER ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Angiotensin Ii ◽  
Baroreflex Sensitivity ◽  
At1 Receptor ◽  
Receptor Blockade ◽  
Double Blind ◽  
Rr Interval

The objective of the present study was to determine the autonomic effects of angiotensin II (AT1) receptor blocker therapy in heart failure. In a randomized double-blind cross-over study, we compared the effects of candesartan and placebo on baroreflex sensitivity and on heart rate variability at rest, during stress and during 24h monitoring. Acute effects were assessed 4h after oral candesartan (8mg) and chronic effects after 4 weeks of treatment (dose titrated to 16mg daily). The study group comprised 21 patients with heart failure [mean (S.E.M.) ejection fraction 33% (1%)], in the absence of angiotensin-converting enzyme (ACE) inhibitor therapy. We found that acute candesartan was not different from placebo in its effects on blood pressure or mean RR interval. Chronic candesartan significantly reduced blood pressure [placebo, 137 (3)/82 (3)mmHg; candesartan, 121 (4)/75 (2)mmHg; P<0.001; values are mean (S.E.M.)], but had no effect on mean RR interval [placebo, 857 (25)ms; candesartan, 857 (21)ms]. Compared with placebo there were no significant effects of acute or chronic candesartan on heart rate variability in the time domain and no consistent effects in the frequency domain. Baroreflex sensitivity assessed by the phenylephrine bolus method was significantly increased after chronic candesartan [placebo, 3.5 (0.5)ms/mmHg; candesartan, 4.8 (0.7)ms/mmHg; P<0.05], although there were no changes in cross-spectral baroreflex sensitivity. Thus, in contrast with previous results with ACE inhibitors, angiotensin II receptor blockade in heart failure did not increase heart rate variability, and there was no consistent effect on baroreflex sensitivity.

scholarly journals P2Y2 receptor activation decreases blood pressure and increases renal Na+ excretion

2011 ◽  
Vol 301 (2) ◽  
pp. R510-R518 ◽  
Author(s):  
Timo Rieg ◽  
Maria Gerasimova ◽  
José L. Boyer ◽  
Paul A. Insel ◽  
Volker Vallon
Keyword(s):  
Blood Pressure ◽  
Urinary Excretion ◽  
Continuous Infusion ◽  
Fractional Excretion ◽  
Receptor Activation ◽  
Maximum Response ◽  
Blood Pressure Responses ◽  
In Vivo Effects ◽  
Endothelial Nitric Oxide

ATP and UTP are endogenous agonists of P2Y2/4 receptors. To define the in vivo effects of P2Y2 receptor activation on blood pressure and urinary excretion, we compared the response to INS45973, a P2Y2/4 receptor agonist and UTP analog, in wild-type (WT) and P2Y2 receptor knockout (P2Y2−/−) mice. INS45973 was administered intravenously as a bolus injection or continuous infusion to determine effects on blood pressure and renal function, respectively. Within seconds, bolus application of INS45973 (0.1 to 3 mg/kg body wt) dose-dependently decreased blood pressure in WT (maximum response −35 ± 2 mmHg) and to a similar extent in endothelial nitric oxide synthase knockout mice. By contrast, blood pressure increased in P2Y2−/− (maximum response +18 ± 1 mmHg) but returned to basal levels within 60 s. Continuous infusion of INS45973 (25 to 750 μg·min−1·kg−1 body wt) dose-dependently increased urinary excretion of Na+ in WT (maximum response +46 ± 15%) but reduced Na+ excretion in P2Y2−/− (maximum responses of −45 ± 15%) mice. In renal clearance experiments, INS45973 did not affect glomerular filtration rate but lowered blood pressure and increased fractional excretion of fluid, Na+, and K+ in WT relative to P2Y2−/− mice. The blood pressure responses to INS45973 are consistent with P2Y2 receptor-mediated NO-independent vasodilation and implicate responses to endothelium-derived hyperpolarizing factor, and P2Y2 receptor-independent vasoconstriction, probably via activation of P2Y4 receptors on smooth muscle. Systemic activation of P2Y2 receptors thus lowers blood pressure and inhibits renal Na+ reabsorption, effects suggesting the potential utility of P2Y2 agonism in the treatment of hypertension.

Safety and Tolerance of Intravenous Nimodipine

1994 ◽  
Vol 28 (10) ◽  
pp. 1143-1148 ◽  
Author(s):  
John J. Sramek ◽  
Allen H. Heller ◽  
Pavur R. Sundaresan ◽  
John Lettieri ◽  
Suzanne Sawin ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Adverse Events ◽  
Normal Population ◽  
Controlled Trial ◽  
Fixed Dose ◽  
Healthy Male ◽  
Peripheral Vein ◽  
Double Blind ◽  
Healthy Male Volunteers ◽  
Male Volunteers

OBJECTIVE: To evaluate the safety and tolerance of intravenous nimodipine administered via a peripheral vein in healthy male volunteers. DESIGN: Double-blind, placebo- and vehicle-controlled trial with three fixed-dose panels. SETTING: Inpatient infusion and observation periods. SUBJECTS: 61 healthy male volunteers, aged 18–40 years. METHODS: Subjects in panel 1 received nimodipine 0.4 mg/h, vehicle 2 mL/h, or placebo 2 mL/h; subjects in panel 2 received nimodipine 1 mg/h, vehicle 5 mL/h, or placebo 5 mL/h; subjects in panel 3 received nimodipine 2 mg/h, vehicle 10 mL/h, or placebo 10 mL/h. All infusions were administered intravenously for 48 hours and volunteers were observed for 48 hours after cessation of the infusion. In addition to standard safety assessments (physical examination, electrocardiogram, laboratory studies, and adverse event reporting), supine and standing blood pressures and pulse rates were measured frequently. Plasma samples were also analyzed for nimodipine and its two demethylated metabolites. RESULTS: Of 61 subjects, 55 completed the 48-hour infusion and 6 discontinued the study because of adverse events. Intravenous nimodipine was well tolerated at 0.4 and 1 mg/h. However, all six subjects who received nimodipine 2 mg/h experienced moderate-to-severe adverse events, and one subject was discontinued because of dizziness, diaphoresis, and postural hypotension. The matched vehicle (10 mL/h) also was not well tolerated, with three subjects who discontinued because of phlebitis. Two subjects who received placebo were also discontinued during the study. Small (2 mm Hg) decreases in mean supine diastolic blood pressure were observed in the 0.4- and 1-mg/h nimodipine groups, but the 2-mg/h group showed a slight (5 mm Hg) increase in blood pressure. These changes were not clinically significant. Clearance and half-life of nimodipine and its metabolites were similar at all three dosages. CONCLUSIONS: Using peripheral vein administration, nimodipine 2 mg/h and matched vehicle at 10 mL/h were not well tolerated in this healthy normal population. The maximum tolerated dose of nimodipine was found to be 1 mg/h.

Sign in / Sign up

Export Citation Format

Share Document