Autonomic nervous control of heart rate in muskrats during exercise in air and under water.

1996 ◽  
Vol 199 (7) ◽  
pp. 1563-1568 ◽  
Author(s):  
P E Signore ◽  
D R Jones
Keyword(s):  
Heart Rate ◽  
Neural Control ◽  
Cardiac Response ◽  
Resting Heart Rate ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Pronounced Increase ◽  
Chronotropic Response ◽  
Autonomic Nervous ◽  
Parasympathetic Tone

Neural control of the cardiac responses to exercise in air (running) and under water (diving) was studied in the muskrat (Ondatra zibethicus) by means of acute pharmacological blockade with the muscarinic blocker atropine and the beta-adrenergic blocker nadolol. Saline injection was used as a control. Controls running on a treadmill showed a marked increase in heart rate with exercise. Atropine-treated animals had a higher resting heart rate than controls, but heart rate still increased with running. Nadolol-treated animals had a lower resting heart rate than controls and displayed a less pronounced increase in heart rate with running than controls. Animals treated with a combination of atropine and nadolol had a resting heart rate similar to that of controls but their heart rate was unaffected by running. Thus, exercise tachycardia in muskrats is due to activation of the sympathetic system and also to a reduction in parasympathetic tone. Heart rate decreased markedly during voluntary submergence in controls but rose as muskrats swam submerged against increasing water flows. Nevertheless, diving bradycardia was still present. Free-diving bradycardia and the relative increase in heart rate with underwater exercise were abolished by atropine and unaffected by nadolol. Hence, unlike the cardiac response to exercise in air, the cardiac response to underwater exercise is due only to a reduction in parasympathetic tone. Injection of the beta-adrenergic agonist isoproterenol markedly increased heart rate in air but had little effect during voluntary and forced dives, indicating a marked decrease in the sensitivity of cardiac cells to adrenergic stimulation during submergence. These results strongly suggest that accentuated antagonism between the two branches of the autonomic nervous system occurs during diving so that parasympathetic influences on the heart predominate and inhibit any chronotropic response to adrenergic stimulation.

Development of autonomic control of fetal circulation

1975 ◽  
Vol 228 (2) ◽  
pp. 337-344 ◽  
Author(s):  
B Nuwayhid ◽  
Brinkman CR ◽  
C Su ◽  
JA Bevan ◽  
NS Assali
Keyword(s):  
Heart Rate ◽  
Cardiovascular Response ◽  
Cardiovascular Responses ◽  
Peripheral Circulation ◽  
Fetal Life ◽  
Resting Heart Rate ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Significant Control ◽  
Parasympathetic System

Development of parasympathetic and sympathetic reflexes controlling heart rate, vascular pressures, and blood flows was investigated in fetal lambs weighing 300-5,800 g (65-165 days' gestation). Cardiovascular responses to veratridine injections, atrial stretching, bilateral cervical vagotomy, and cholinergic blockade with atropine were used to test parasympathetic activities. Responses to propranolol and phenoxybenzamine were used to test beta- and alpha-adrenergic activities. Autonomic ganglionic blockade and stimulation provided additional information on both cholinergic and adrenergic systems. Fetal responses to various tests were compared to those of the mother. Results show: a) little parasympathetic tone on resting heart rate and other circulatory functions exists prior to fetal maturity; b) despite the feeble resting tone, the parasympathetic system is capable of exerting significant control when stimulated in both premature and mature fetuses, the capability increases as fetus approaches term; c) alpha- and beta-adrenergic tone in control of resting heart rate and peripheral circulation exists in early fetal life and increases as the fetus reaches maturity, and both adrenergic receptors respond strongly to stimuli in immature, premature, and mature fetuses; d) in immature fetuses, veratridine does not elicit a vagally mediated reflex; instead, it produces a centrally mediated alpha- and beta-adrenergic stimulation; e) the fetal cardiovascular response to any given test is dampened by the existence of the various vascular shunts, the umbilicoplacental circulation and, possibly, by incomplete maturation of vasomotor tone.

Cardiac function and chronotropic sensitivity to beta-adrenergic stimulation in sepsis

1986 ◽  
Vol 251 (2) ◽  
pp. H405-H412 ◽  
Author(s):  
L. W. Smith ◽  
S. L. Winbery ◽  
L. A. Barker ◽  
K. H. McDonough
Keyword(s):  
Heart Rate ◽  
Myocardial Function ◽  
Cardiovascular Response ◽  
Maximal Heart Rate ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Chronotropic Response ◽  
Arterial Blood ◽  
Perfused Hearts ◽  
Right Atria

An organism's cardiovascular response to sepsis is at least partly dependent on hormonal and neural modulation of myocardial function. We have investigated both intrinsic myocardial performance and one aspect of myocardial sensitivity to beta-adrenergic stimulation in a model of sepsis in which animals, at the time studied, exhibited bacteremia, normal arterial blood pressure and cardiac output, elevated heart rate, and elevated plasma catecholamines. Intrinsic myocardial contractile function, studied with the isolated, perfused working heart preparation, was depressed over a range of preloads in septic animals, whereas heart rate was elevated. To determine whether hearts from septic animals could respond normally to beta-adrenergic stimulation, we studied chronotropic responses to isoproterenol in both Langendorff perfused hearts and in isolated right atria. In langendorff perfused hearts from septic animals, basal rates were significantly increased and lower concentrations of isoproterenol elicited greater increases in heart rate. In isolated right atria from septic animals, basal rates were also elevated and the EC50 for the chronotropic response to isoproterenol was significantly less than in atria from control animals. The maximal heart rate response to isoproterenol was not significantly different from control. These results indicate that in sepsis, despite apparently adequate in vivo cardiac performance, intrinsic myocardial function is depressed, but chronotropic sensitivity to beta-adrenergic stimulation is increased.

Decreased cardiac response to isoproterenol infusion in acute and chronic hypoxia

1988 ◽  
Vol 65 (5) ◽  
pp. 1957-1961 ◽  
Author(s):  
J. P. Richalet ◽  
P. Larmignat ◽  
C. Rathat ◽  
A. Keromes ◽  
P. Baud ◽  
...  
Keyword(s):  
Heart Rate ◽  
Adrenergic Receptors ◽  
Chronic Hypoxia ◽  
Diastolic Pressure ◽  
Acute Hypoxia ◽  
Cardiac Response ◽  
Beta Adrenergic Receptors ◽  
Beta Adrenergic ◽  
Chronotropic Response ◽  
Isoproterenol Infusion

The hypothesis of a blunted chronotropic response of cardiac beta-adrenergic receptors in altitude hypoxia was tested in nine subjects at sea level (SL) by infusion of isoproterenol. Observations were made at SL, in acute hypoxia (2 days at 4,350 m, condition H1), in more prolonged hypoxia [13 days between 850 and 4,800 m, condition H2] and in chronic hypoxia [21 days at 4,800 m, condition H3]. Resting heart rate was higher in all hypoxic conditions. Resting norepinephrine concentrations were found to be significantly higher in conditions H2 (1.64 +/- 0.59) and H3 (1.74 +/- 0.76) than at SL (0.77 +/- 0.18 ng/ml). Isoproterenol, diluted in saline, was infused at increasing doses of 0.0, 0.02, 0.04, and 0.06 micrograms.kg-1.min-1. For the highest dose, there was a significantly smaller increase in heart rate in conditions H1 (35 +/- 9), H2 (33 +/- 11), and H3 (31 +/- 11) than at SL (45 +/- 8 min-1). The increase in pulse (systolic/diastolic) pressure, considered as the vascular response to isoproterenol infusion, was smaller in condition H3 (29 +/- 16) than at SL (51 +/- 24 mmHg). There was a significant increase in the dose of isoproterenol required to increase heart rate by 25 min-1 and decrease in slope of heart rate increase vs. log(dose) relationship in conditions H2 and H3. Thus an hypoxia-related attenuated response of beta-adrenergic receptors to exogenous stimulation was found in humans.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of the heart rate profile during exercise in patients with atrial fibrillation

2018 ◽  
Vol 25 (15) ◽  
pp. 1634-1641 ◽  
Author(s):  
Kazufumi Aihara ◽  
Yuko Kato ◽  
Shinya Suzuki ◽  
Takuto Arita ◽  
Naoharu Yagi ◽  
...  
Keyword(s):  
Heart Failure ◽  
Atrial Fibrillation ◽  
Heart Rate ◽  
Sinus Rhythm ◽  
Exercise Capacity ◽  
Resting Heart Rate ◽  
Peak Heart Rate ◽  
Chronotropic Response ◽  
Response Peak ◽  
Rate Profile

Aims This study aimed to investigate the correlation of heart rate profile during exercise with exercise capacity and heart failure occurrence in patients with atrial fibrillation compared with patients with sinus rhythm. Methods We analyzed 2231 patients (atrial fibrillation: n = 321, sinus rhythm: n = 1910) who underwent a symptom-limited maximal cardiopulmonary exercise test at our institute. Their heart rate profile during exercise was assessed using peak heart rate and chronotropic response; (peak heart rate−resting heart rate)/(220−age−resting heart rate). The endpoint was the occurrence of heart failure events, defined as hospitalization for heart failure or heart failure-related death. Results There were significant positive correlations of peak heart rate and chronotropic response to peak oxygen consumption, both in atrial fibrillation and sinus rhythm. During a median follow-up period of 1262 (interquartile range 974–2921) days, 117 (5.2%) heart failure events were observed. Multivariate analyses showed that peak heart rate and chronotropic response were statistically significant predictors of heart failure events both in atrial fibrillation (peak heart rate: heart rate 0.975, p = 0.002, chronotropic response: heart rate 0.196, p = 0.003) and in sinus rhythm (peak heart rate: heart rate 0.988, p = 0.036, chronotropic response: heart rate 0.347, p = 0.020). Bivariate models showed that compared with chronotropic response, peak heart rate was a stronger predictor of heart failure in atrial fibrillation, whereas the finding was reversed in sinus rhythm. Conclusion The exercise- heart rate profile was significantly related to exercise capacity and future heart failure events, regardless of rhythm. However, the impacts of peak heart rate and chronotropic response on the endpoint varied according to the cardiac rhythm.

Autonomic nervous system tests depend on resting heart rate and blood pressure

1991 ◽  
Vol 35 (1) ◽  
pp. 15-24 ◽  
Author(s):  
J.Gert van Dijk ◽  
Monique Koenderink ◽  
Aeilko H. Zwinderman ◽  
Joost Haan ◽  
Cor G.S. Kramer ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Nervous System ◽  
Autonomic Nervous System ◽  
Resting Heart Rate ◽  
Autonomic Nervous

scholarly journals Resting heart rate and cardiac autonomic tone during passive head-up tilt: a cross-sectional study in 569 subjects without cardiovascular diseases​

2019 ◽  
Author(s):  
Jenni Koskela ◽  
Anna Tahvanainen ◽  
Antti Tikkakoski ◽  
Pauliina Kangas ◽  
Marko Uitto ◽  
...  
Keyword(s):  
Heart Rate ◽  
Cardiovascular Diseases ◽  
Whole Body ◽  
Sympathovagal Balance ◽  
Resting Heart Rate ◽  
Autonomic Tone ◽  
Cross Sectional ◽  
Pronounced Increase ◽  
Head Up Tilt ◽  
Hrv Analysis

Abstract Background Resting heart rate (HR) and its variability (HRV) reflect cardiac sympathovagal balance that can stimulated by head-up tilting. HRV is significantly influenced by the level of HR, but how much HRV offers additional information about cardiac autonomic tone than HR alone remains unresolved. We examined the relation of resting HR with short term HRV during passive head-up tilt.Methods Hemodynamics of 569 subjects without medications with direct cardiovascular effects and known cardiovascular diseases were recorded using whole-body impedance cardiography, continuous radial pulse wave analysis and electrocardiography based HRV analysis in supine and upright positions. For statistical analyses the study population was divided into tertiles of resting heart rate according to sexes.Results Higher low frequency to high frequency ratio (LF/HF) of HRV (reflecting sympathovagal balance) was associated with higher HR in supine (p<0.001) and upright positions (p=0.008). The outcome was similar when the HRV analysis was based on HR instead of RR-intervals (p<0.001 supine, p=0.012 upright). The lowest HR tertile presented with higher supine to upright increase in LF/HF than the highest HR tertile (1.1 vs. 0.85, respectively, p=0.037).Conclusion Higher resting HR is related to higher LF/HF in supine and upright positions, reflecting higher cardiac sympathovagal balance. Lower resting HR is associated with lower resting LF/HF, but with a more pronounced increase in both HR and LF/HF during head-up tilt, suggesting greater change cardiac sympathovagal balance in response to upright posture.

scholarly journals Beta-adrenergic Receptor Blockade Effects on Cardio-pulmonary Exercise Testing

2021 ◽  
Author(s):  
Kevin Forton ◽  
Michel Lamotte ◽  
Alexis Gillet ◽  
Martin Chaumont ◽  
Van De Borne Philippe ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Single Dose ◽  
Adrenergic Receptor ◽  
Adrenergic Blockade ◽  
Receptor Blockade ◽  
Beta Adrenergic Receptor ◽  
Beta Adrenergic ◽  
Chronotropic Response ◽  
Adrenergic Receptor Blockade

Abstract Background: Beta-blockers are increasingly prescribed while the effects of beta-adrenergic receptor blockade on cardio-pulmonary exercise test (CPET) derived parameters remain under-studied. Methods: 21 young healthy adults repeated 3 CPET at an interval of 7 days at the same time of the day. The tests were performed 3 hours after a random, double blind, cross-over single dose intake of placebo, 2.5 mg bisoprolol or 5 mg bisoprolol. Gaz exchange, heart rate and blood pressure were measured at rest and during cyclo-ergometric CPET.Results: Maximal workload and VO2max were unaffected by the treatment, with maximal respiratory exchange ratio > 1.15 in all tests. A beta-blocker dose-dependent effect reduced resting and maximal blood pressure and heart rate and the chronotropic response to exercise, evaluated by the heart rate/VO2 slope (placebo: 2,9 ± 0,4 beat/ml/kg; 2,5 mg bisoprolol: 2,4 ± 0,5 beat/ml/kg; 5 mg bisoprolol: 2,3 ± 0,4 beat/ml/kg, p<0.001). Ventilation efficiency measured by the VE/VCO2 slope and the ventilatory equivalent for CO2 at the ventilatory threshold were not affected by beta1-receptor blockade. Post-exercise chronotropic recovery measured after 1 min was enhanced under beta1-blocker (placebo: 26 ± 7 bpm; 2,5 mg bisoprolol: 32 ± 6 bpm; 5 mg bisoprolol: 33 ± 6 bpm, p<0.01).Conclusion: The present results suggest that a single dose of bisoprolol does not affect metabolism, respiratory response and exercise capacity. However, beta-adrenergic blockade dose-dependently reduced exercise hemodynamic response by lowering the pressure and chronotropic responses.

Beta-adrenergic effects on left ventricular filling: influence of aging and exercise training

1994 ◽  
Vol 77 (6) ◽  
pp. 2522-2529 ◽  
Author(s):  
J. R. Stratton ◽  
W. C. Levy ◽  
R. S. Schwartz ◽  
I. B. Abrass ◽  
M. D. Cerqueira
Keyword(s):  
Heart Rate ◽  
Endurance Training ◽  
Left Ventricular ◽  
Beta Agonist ◽  
Diastolic Filling ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
End Diastolic Volume ◽  
Before And After ◽  
Ventricular Filling

Reduced heart rate and contractile responses to beta-agonist stimulation characterize normal cardiac aging, but whether diastolic responses also decline with aging has not been determined in humans. Diastolic filling responses to isoproterenol were determined in 13 older (60–82 yr) and 11 young (24–32 yr) healthy men before and after endurance training. Filling rates were expressed in three ways: 1) normalized to end-diastolic volume per second, 2) normalized to stroke volume per second, and 3) as absolute milliliters of blood (ml.s-1.m-2). Peak early filling rates by all methods were reduced at rest and all isoproterenol doses with aging (all P < 0.0001 for old vs. young), whereas peak atrial filling rates were increased with aging. During isoproterenol, both peak early and peak atrial filling rates increased significantly (all P < 0.01); the increase in filling rates with isoproterenol was not different with aging (all NS for old vs. young x dose). Endurance training did not augment diastolic filling responses to isoproterenol. Although diastolic filling rates at rest are markedly altered by aging, diastolic filling responses to isoproterenol are not reduced with aging. Thus the age-associated declines in heart rate, ejection fraction, and cardiac output responses to beta-adrenergic stimulation with isoproterenol do not extend to diastolic filling responses.

Cardiac response to startle stimuli in larval zebrafish: sympathetic and parasympathetic components

2010 ◽  
Vol 298 (5) ◽  
pp. R1288-R1297 ◽  
Author(s):  
Kara D. Mann ◽  
Carlton Hoyt ◽  
Shaina Feldman ◽  
LaChelle Blunt ◽  
Aaron Raymond ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Cardiac Output ◽  
Autonomic Nervous System ◽  
Sudden Onset ◽  
Cardiac Response ◽  
Autonomic Nervous ◽  
Repeated Stimulation ◽  
Larval Zebrafish ◽  
Transient Bradycardia

Central regulation of cardiac output via the sympathetic and parasympathetic branches of the autonomic nervous system allows the organism to respond to environmental changes. Sudden onset stimuli, startle stimuli, are useful probes to study central regulatory responses to the environment. In mammals, startle stimuli induce a transient bradycardia that habituates with repeated stimulation. Repeated presentation of the stimulus results in tachycardia. In this study, we investigate the behavioral regulation of heart rate in response to sudden stimuli in the zebrafish. Larval zebrafish show a stereotyped heart rate response to mild electrical shock. Naïve fish show a significant increase in interbeat interval that resolves in the 2 s following stimulation. This transient bradycardia decreases on repeated exposure to the stimulus. Following repeated stimulation, the fish become tachycardic within 1 min of stimulation. Both the transient bradycardia and following tachycardia responses are blocked with administration of the ganglionic blocker hexamethonium, demonstrating that these responses are mediated centrally. The transient bradycardia is blocked by the muscarinic antagonist atropine, suggesting that this response is mediated by the parasympathetic system, while the following tachycardia is specifically blocked by the beta-adrenergic antagonist propranolol, suggesting that this response is mediated by the sympathetic nervous system. Together, these results demonstrate that at the larval stage, zebrafish actively regulate cardiac output to changes in their environment using both the parasympathetic and sympathetic branches of the autonomic nervous system, a behavioral response that is markedly similar to that observed in mammals to similar sudden onset stimuli.

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