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The American Journal of Physiology Apr 1996To study heart rate baroreflex gain, autoregressive moving average (ARMA) analysis, a multivariate method that allows evaluation of the dynamic ("beat-to-beat")... (Comparative Study)
Comparative Study
To study heart rate baroreflex gain, autoregressive moving average (ARMA) analysis, a multivariate method that allows evaluation of the dynamic ("beat-to-beat") interactions between changes in biological signals, was used to evaluate the relationships between R-R interval and arterial blood pressure (BP) during random-interval breathing. Parameters obtained by ARMA analysis of spontaneous fluctuations in BP and R-R interval in 17 volunteers were used to model the response of R-R interval to a transient 1-mmHg increase in BP; the resulting impulse-response and step-response curves were compared with baroreflex gain measured using bolus injections of phenylephrine (PE) and sodium nitroprusside (SNP). Impulse-response curves for the systolic BP-R-R relationship showed an early (0-1 s) sharp maximum of 5.5 +/- 4.2 ms/mmHg, which was smaller in magnitude but linearly correlated with baroreflex gain derived from SNP (14.5 +/- 9.7 ms/mmHg; r = 0.80, P < 0.002) and PE (31.6 +/- 26.7 ms/mmHg; r = 0.53, P < 0.05) injections. A similar relationship was also found between the one-beat ARMA step response and SNP injection (r = 0.70, P = 0.01). The integrated step response of the BP-R-R relationship over 6 s was 6.4 +/- 4.1 ms/mmHg, with no correlation to baroreflex gain determined by SNP (r = 0.33, P = 0.20) or PE (r = -0.15, P = 0.57). In conclusion, quantification of baroreflex gain consistent with other techniques may be achieved by ARMA analysis without perturbing mean BP. Correlation of baroreflex gain obtained by bolus injection to early measures of baroreflex gain obtained from the ARMA maximum impulse and early step responses, but not the late step response, suggests that the ARMA method may provide additional information regarding the frequency dependent effects of BP on R-R-interval.
Topics: Adolescent; Adult; Blood Pressure; Cardiology; Female; Heart Rate; Humans; Injections, Intravenous; Male; Models, Cardiovascular; Nitroprusside; Phenylephrine; Pressoreceptors
PubMed: 8967362
DOI: 10.1152/ajpheart.1996.270.4.H1240 -
The American Journal of Physiology Nov 1982It has been recently reported that intracoronary acetylstrophanthidin injection acutely sensitizes the cardiac baroreflex (vagal afferents). We wondered whether chronic...
It has been recently reported that intracoronary acetylstrophanthidin injection acutely sensitizes the cardiac baroreflex (vagal afferents). We wondered whether chronic administration of digoxin also augmented the gain of this reflex. We treated seven dogs with digoxin intravenously (40 micrograms/kg loading dose followed by 15 micrograms.kg-1.day-1) for 7 days; eight additional dogs received vehicle for 7 days. With the dogs under chloralose anesthesia, we assessed the changes in renal nerve activity that resulted from stimulation of cardiopulmonary receptors with volume expansion (15 ml/kg of 6% dextran in saline) in digoxin- and vehicle-treated groups under control conditions, after sinoaortic denervation (SAD), and after SAD plus vagotomy. Under control conditions volume expansion resulted in decreases of renal nerve activity of 13.5 +/- 3.5%/mmHg increase in pulmonary artery wedge pressure in digoxin-treated dogs. This tended to be greater than the response of sham-treated dogs (-9.5 +/- 1.5%/mmHg increase). After SAD, renal nerve activity decreased 19 +/- 5%/mmHg increase in pulmonary artery wedge pressure in the digoxin group compared with only 8 +/- 1%/mmHg increase in the vehicle group. These responses were significantly different. The plasma digoxin level in the digoxin-treated group was in the therapeutic range (1.9 +/- 0.4 ng/ml). Vagotomy abolished the responses to volume expansion in both groups. Thus chronic digoxin treatment resulting in therapeutic plasma levels of digoxin sensitizes vagal afferents mediating the cardiopulmonary baroreflex influence on renal nerve activity.
Topics: Animals; Digoxin; Dogs; Heart Conduction System; Kidney; Lung; Peripheral Nerves; Pressoreceptors; Vagotomy; Vagus Nerve
PubMed: 7137374
DOI: 10.1152/ajpheart.1982.243.5.H815 -
Hypertension (Dallas, Tex. : 1979) Feb 1990
Topics: Animals; Atrial Natriuretic Factor; Pressoreceptors; Rats; Reflex; Sympathetic Nervous System; Vagus Nerve
PubMed: 2137428
DOI: 10.1161/01.hyp.15.2.168 -
Acta Physiologica Scandinavica.... 1988
Review
Topics: Animals; Blood Circulation; Humans; Hypertension; Neurotransmitter Agents; Pressoreceptors
PubMed: 2907228
DOI: No ID Found -
Acta Physiologica Scandinavica Apr 1977The characteristics of 40 C-fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between...
The characteristics of 40 C-fibres arising from the aortic arches of 15 normotensive rabbits have been investigated. The conduction velocity of the fibres varied between 0.5-1.8 m/s (0.91 +/- 0.05, mean +/- S.E.). The activation threshold for all the fibres lay between 70-140 mmHg. 32 medullated fibres from the same animals had thresholds between 35 and 90 mmHg. After correction for the time delay in conduction the firing in the C-fibres occurs in early systole. Pressure response curves were constructed for 10 medullated and 18 C-fibres. The mean activity at 100 mmHg was, for the C-fibres 5.0 Hz and for the medullated fibres 34 Hz. At 130 mmHg the activity in the C-fibres was 13 Hz and in the medullated fibres 68 Hz. Thus C-fibres from the aortic baroreceptor regions are activated at higher pressures than the medullated fibres and have lower discharge frequencies. Noradrenaline did not influence the pressure response curves of the C-fibres. It is concluded that the arterial baroreceptor C-fibres may exert a weak tonic influence on the vasomotor centre at normal pressures but are likely to be of greater importance when the arterial pressure rises acutely.
Topics: Animals; Aorta, Thoracic; Blood Pressure; Electric Stimulation; Nerve Fibers; Neural Conduction; Norepinephrine; Pressoreceptors; Rabbits
PubMed: 855672
DOI: 10.1111/j.1748-1716.1977.tb10397.x -
Clinical Physiology and Biochemistry 1990The antihypertensive action of angiotensin-converting enzyme (ACE) inhibitors may be related to inhibition of systemic and local vascular angiotensin-II formation, to a... (Review)
Review
The antihypertensive action of angiotensin-converting enzyme (ACE) inhibitors may be related to inhibition of systemic and local vascular angiotensin-II formation, to a potentiation of the local vascular kinin system with secondary stimulation of prostacyclin synthesis, and also to their effects on the central nervous system as well as on renal hemodynamics and excretory function. More detailed studies in patients with severe hypertension, previously not adequately controlled by conventional therapy with a diuretic, a beta-blocking agent and a vasodilator dihydralazine, showed that addition of the ACE inhibitor ramipril normalized systolic and diastolic blood pressure (BP) without hypotensive episodes or reflex tachycardia. ACE inhibition caused a change in the baroreceptor set point as we had previously demonstrated in healthy subjects, but baroreceptor sensitivity was not affected and the pressure response to exogenous norepinephrine remained unchanged by ACE inhibition. Despite the significant reduction in BP in our patients, endogenous creatinine clearance remained unaltered. Furthermore, the decrease in BP is accompanied by an initial natriuresis probably contributing to the BP-lowering effect of ACE inhibitors. Decreased proximal tubular reabsorption may include enhanced urate clearance reflected by a decrease in serum urate concentration which we observed despite continuous diuretic treatment. ACE inhibition also prevents secondary aldosteronism and thereby avoids renal potassium loss. In our patients this resulted in a 10% decrease in urinary potassium excretion and a small rise in serum potassium concentration. Redistribution of intrarenal blood flow with increased medullary flow, in addition, will antagonize the hydroosmotic effect of vasopressin, thus resulting in a rise in free-water clearance.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Acid-Base Equilibrium; Angiotensin-Converting Enzyme Inhibitors; Blood Pressure; Humans; Hypertension; Kidney Tubules; Pressoreceptors; Renal Circulation
PubMed: 2257720
DOI: No ID Found -
Journal of Applied Physiology Sep 1976Carotid baroreceptors were stimulated with graded neck suction in supine and standing volunteers, before and after autonomic blockade, to determine the influence of...
Carotid baroreceptors were stimulated with graded neck suction in supine and standing volunteers, before and after autonomic blockade, to determine the influence of posture on baroreflex responsiveness. Propranolol significantly augmented baroreflex pulse interval prolongation in the supine position. Upright posture did not modify baroreflex pulse interval responses prior to propranolol, but significantly augmented responses after propranolol. The results suggest that standing enhances baroreflex sensitivity, but that under normal circumstances, this effect is masked by beta-adrenergic stimulation. Augmentation of baroreflex pulse interval prolongation in the supine and standing positions by propranolol may contribute to the effectiveness of this drug in angina pectoris and labile hypertension.
Topics: Adult; Atropine; Carotid Sinus; Female; Heart Rate; Humans; Male; Posture; Pressoreceptors; Propranolol
PubMed: 965307
DOI: 10.1152/jappl.1976.41.3.383 -
Journal of Cardiac Failure Jun 2011Studies have shown that the autonomic dysfunction accompanied by impaired baroreflex sensitivity was associated with higher mortality. However, the influence of...
BACKGROUND
Studies have shown that the autonomic dysfunction accompanied by impaired baroreflex sensitivity was associated with higher mortality. However, the influence of decreased baroreflex sensitivity on cardiac function, especially in diastolic function, is not well understood. This study evaluated the morphofunctional changes associated with baroreflex impairment induced by chronic sinoaortic denervation (SAD).
METHODS AND RESULTS
Animals were divided into sinoaortic denervation (SAD) and control (C) groups. Baroreflex sensitivity was evaluated by tachycardic and bradycardic responses, induced by vasoactive drugs. Cardiac function was studied by echocardiography and by left ventricle (LV) catheterization. LV collagen content and the expression of regulatory proteins involved in intracellular Ca(2+) homeostasis were quantified. Results showed higher LV mass in SAD versus C animals. Furthermore, an increase in deceleration time of E-wave in the SAD versus the C group (2.14 ± 0.07 ms vs 1.78 ± 0.03 ms) was observed. LV end-diastolic pressure was increased and the minimum dP/dt was decreased in the SAD versus the C group (12 ± 1.5 mm Hg vs 5.3 ± 0.2 mm Hg and 7,422 ± 201 vs 4,999 ± 345 mm Hg/s, respectively). SERCA/NCX ratio was lower in SAD than in control rats. The same was verified in SERCA/PLB ratio.
CONCLUSIONS
The results suggest that baroreflex dysfunction is associated with cardiac diastolic dysfunction independently of the presence of other risk factors.
Topics: Animals; Baroreflex; Denervation; Disease Models, Animal; Heart Failure, Diastolic; Male; Pressoreceptors; Rats; Rats, Wistar; Risk Factors; Ventricular Dysfunction, Left
PubMed: 21624741
DOI: 10.1016/j.cardfail.2011.02.007 -
The Journal of Physiology Aug 2011In contrast to the reflex vasodilatation occurring in response to stimulation of baroreceptors in the aortic arch, carotid sinuses and coronary arteries, stimulation of... (Comparative Study)
Comparative Study
In contrast to the reflex vasodilatation occurring in response to stimulation of baroreceptors in the aortic arch, carotid sinuses and coronary arteries, stimulation of receptors in the wall of pulmonary arteries results in reflex systemic vasoconstriction. It is rare for interventions to activate only one reflexogenic region, therefore we investigated how these two types of reflexes interact. In anaesthetized dogs connected to cardiopulmonary bypass, reflexogenic areas of the carotid sinuses, aortic arch and coronary arteries and the pulmonary artery were subjected to independently controlled pressures. Systemic perfusion pressure (SPP) measured in the descending aorta (constant flow) provided an index of systemic vascular resistance. In other experiments, sympathetic efferent neural activity was recorded in fibres dissected from the renal nerve (RSNA). Physiological increases in pulmonary arterial pressure (PAP) induced significant increases in SPP (+39.1 ± 10.4 mmHg) and RSNA (+17.6 ± 2.2 impulses s(−1)) whereas increases in carotid sinus pressure (CSP) induced significant decreases in SPP (−42.6 ± 10.8 mmHg) and RSNA (−42.8 ± 18.2 impulses s(−1)) (P < 0.05 for each comparison; paired t test). To examine possible interactions, PAP was changed at different levels of CSP in both studies. With CSP controlled at 124 ± 2 mmHg, the threshold, 'set point' and saturation pressures of the PAP–SPP relationship were higher than those with CSP at 60 ± 1 mmHg; this rightward shift was associated with a significant decrease in the reflex gain. Similarly, increasing CSP produced a rightward shift of the PAP–RSNA relationship, although the effect on reflex gain was inconsistent. Furthermore, the responses to changes in CSP were influenced by setting PAP at different levels; increasing the level of PAP from 5 ± 1 to 33 ± 3 mmHg significantly increased the set point and threshold pressures of the CSP–SPP relationship; the reflex gain was not affected. These results indicate the existence of interaction between pulmonary arterial and carotid sinus baroreceptor reflexes; physiological and pathological states that alter the stimulus to one may alter the reflex responses from the other.
Topics: Animals; Baroreflex; Carotid Sinus; Dogs; Female; Perfusion; Pressoreceptors; Pulmonary Artery; Vasoconstriction
PubMed: 21690195
DOI: 10.1113/jphysiol.2011.210732 -
Brain Research Bulletin Jan 2000
Topics: Animals; Baroreflex; Medulla Oblongata; Neural Pathways; Neuropeptides; Neurotransmitter Agents; Pressoreceptors; Rats
PubMed: 10709953
DOI: 10.1016/s0361-9230(99)00262-2