Autonomic mechanisms of muscle metaboreflex control of heart rate

1993 ◽  
Vol 74 (4) ◽  
pp. 1748-1754 ◽  
Author(s):  
D. S. O'Leary
Keyword(s):  
Heart Rate ◽  
Sympathetic Activity ◽  
Perfusion Pressure ◽  
Systemic Arterial Pressure ◽  
Open Loop ◽  
Loop Gain ◽  
Post Exercise ◽  
Muscle Metaboreflex ◽  
Muscle Ischemia ◽  
Before And After

Ischemia in active skeletal muscle induces reflex increases in systemic arterial pressure (SAP) and heart rate (HR), termed the muscle metaboreflex. When metaboreflex activation is maintained during postexercise muscle ischemia, SAP remains elevated; however, HR decreases. Why the HR responses differ with metaboreflex activation during exercise vs. during postexercise ischemia while the SAP responses are similar in each setting remains unclear. Two hypotheses were tested: 1) the increase in HR with muscle ischemia occurs predominantly via an increase in sympathetic activity, and 2) sympathetic activity to the heart remains elevated during post-exercise ischemia; however, HR decreases because of an increase in parasympathetic outflow. The muscle metaboreflex was activated in conscious dogs during treadmill exercise (3.2 kph, 0% grade) by progressively decreasing perfusion to the hindlimbs. Experiments were performed before and after muscarinic (atropine) or beta- (atenolol or propranolol) receptor blockade. In control experiments, once beyond the threshold for the reflex, the HR sensitivity of the muscle metaboreflex averaged -2.4 +/- 0.3 beats.min-1.mmHg-1 and the reflex open-loop gain averaged -3.2 +/- 0.3 (calculated as the ratio of the increase in HR or SAP to the decrease in hindlimb perfusion pressure beyond threshold). Atropine had no effect on either HR sensitivity (-2.7 +/- 0.4 beats.min-1.mmHg-1) or open-loop gain (-3.3 +/- 0.5, both P > 0.05 vs. control). However, pretreatment with beta-receptor antagonist significantly decreased both HR sensitivity (-0.7 +/- 0.1 beats.min-1.mmHg-1, P < 0.001) and open-loop gain (-1.9 +/- 0.3, P < 0.01). During postexercise ischemia, HR decreased while SAP remained elevated.(ABSTRACT TRUNCATED AT 250 WORDS)

Baroreflex attenuates pressor response to graded muscle ischemia in exercising dogs

1990 ◽  
Vol 258 (2) ◽  
pp. H305-H310 ◽  
Author(s):  
D. D. Sheriff ◽  
D. S. O'Leary ◽  
A. M. Scher ◽  
L. B. Rowell
Keyword(s):  
Perfusion Pressure ◽  
Pressor Response ◽  
Vascular Occlusion ◽  
Arterial Baroreceptors ◽  
Systemic Pressure ◽  
Muscle Ischemia ◽  
Pressor Responses ◽  
Before And After ◽  
Muscle Chemoreflex ◽  
Arterial Baroreceptor

Graded reductions in hindlimb perfusion in dogs exercising at 2 miles/h (0% grade) elicited reflex pressor responses by what is referred to as the “muscle chemoreflex.” To determine the extent to which arterial baroreceptor reflexes oppose the muscle chemoreflex, we elicited pressor responses to muscle ischemia before and after chronic surgical denervation of the arterial baroreceptors. The muscle chemoreflex showed a threshold beyond which systemic pressure rose approximately 3 mmHg for each 1-mmHg decrease in hindlimb perfusion pressure when the arterial baroreceptors were intact. Arterial baroreceptor denervation approximately doubled the pressor responses, i.e., systemic pressure rose by approximately 6 mmHg for each 1-mmHg fall in hindlimb perfusion pressure, without alteration in threshold. We conclude that during mild dynamic exercise, the arterial baroreflexes oppose the pressor response to graded reductions in hindlimb perfusion, reducing it by approximately 50%. When unopposed by the arterial baroreflexes the muscle chemoreflex exhibits a gain (ratio of change in systemic pressure to change in hindlimb perfusion pressure) of approximately -6; thus this reflex can correct by 85% the decrease in muscle perfusion pressure caused by partial vascular occlusion.

scholarly journals Attenuated muscle metaboreflex-induced pressor response during postexercise muscle ischemia in renovascular hypertension

2015 ◽  
Vol 308 (7) ◽  
pp. R650-R658 ◽  
Author(s):  
Marty D. Spranger ◽  
Jasdeep Kaur ◽  
Javier A. Sala-Mercado ◽  
Tiago M. Machado ◽  
Abhinav C. Krishnan ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Pressor Response ◽  
Dynamic Exercise ◽  
Hindlimb Ischemia ◽  
Muscle Metaboreflex ◽  
Muscle Ischemia ◽  
Normal Individuals ◽  
Before And After ◽  
Exercise Muscle ◽  
Sustained Increase

During dynamic exercise, muscle metaboreflex activation (MMA; induced via partial hindlimb ischemia) markedly increases mean arterial pressure (MAP), and MAP is sustained when the ischemia is maintained following the cessation of exercise (postexercise muscle ischemia, PEMI). We previously reported that the sustained pressor response during PEMI in normal individuals is driven by a sustained increase in cardiac output (CO) with no peripheral vasoconstriction. However, we have recently shown that the rise in CO with MMA is significantly blunted in hypertension (HTN). The mechanisms sustaining the pressor response during PEMI in HTN are unknown. In six chronically instrumented canines, hemodynamic responses were observed during rest, mild exercise (3.2 km/h), MMA, and PEMI in the same animals before and after the induction of HTN [Goldblatt two kidney, one clip (2K1C)]. In controls, MAP, CO and HR increased with MMA (+52 ± 6 mmHg, +2.1 ± 0.3 l/min, and +37 ± 7 beats per minute). After induction of HTN, MAP at rest increased from 97 ± 3 to 130 ± 4 mmHg, and the metaboreflex responses were markedly attenuated (+32 ± 5 mmHg, +0.6 ± 0.2 l/min, and +11 ± 3 bpm). During PEMI in HTN, HR and CO were not sustained, and MAP fell to normal recovery levels. We conclude that the attenuated metaboreflex-induced HR, CO, and MAP responses are not sustained during PEMI in HTN.

scholarly journals Perturbations of Adjuvant Chemotherapy on Cardiovascular Responses and Exercise Tolerance in Patients with Early-Stage Breast Cancer

Biology ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 910
Author(s):  
Hsin-Fu Lin ◽  
Ching-Ying Tseng ◽  
Toby Mündel ◽  
Yi-Yuan Lin ◽  
Chung-Chi Lin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Heart Rate ◽  
Exercise Tolerance ◽  
Early Stage ◽  
Heart Rate Recovery ◽  
Cardiovascular Responses ◽  
Early Stage Breast Cancer ◽  
Exercise Heart Rate ◽  
Post Exercise ◽  
Before And After

Background: Adjuvant chemotherapies are commonly used for treating early-stage breast cancer. However, whether chemotherapeutic regimens affect exercise tolerance and cardiovascular responses remains unclear. Therefore, we investigated the effects of receiving CAF and AC-T on exercise tolerance and cardiovascular responses in patients with early-stage breast cancer. Methods: Thirty-four patients with breast cancer (age: 44 ± 1 years; stage I-II) received either CAF (n = 15) or AC-T (n = 19), depending on clinical decisions. Their step-exercise tolerance and cardiovascular responses were assessed before and after chemotherapy. Results: After chemotherapy, there were no differences in baseline measurements between patients receiving CAF or AC-T. The increases in resting heart rate (RHR) of those receiving AC-T was significantly greater than that of those receiving CAF. CAF and AC-T did not result in increased pulse wave velocity (PWV), yet the subendocardial viability ratio (SEVR) in patients receiving AC-T was significantly lower than the baseline. Greater change in post-exercise heart rate recovery (recovery HR) after chemotherapy was observed in those who had received AC-T; the Recovery HR in AC-T patients was significantly higher during post-exercise period than that in CAF patients. Conclusions: AC-T chemotherapy increases RHR and impairs exercise tolerance after chemotherapy more than CAF. Moreover, AC-T also lowers myocardial perfusion more than CAF after chemotherapy.

High-cut characteristics of the baroreflex neural arc preserve baroreflex gain against pulsatile pressure

2002 ◽  
Vol 282 (3) ◽  
pp. H1149-H1156 ◽  
Author(s):  
Toru Kawada ◽  
Can Zheng ◽  
Yusuke Yanagiya ◽  
Kazunori Uemura ◽  
Tadayoshi Miyamoto ◽  
...  
Keyword(s):  
Heart Rate ◽  
Transfer Function ◽  
Sympathetic Nerve Activity ◽  
Dynamic Range ◽  
Open Loop ◽  
Loop Gain ◽  
Frequency Range ◽  
Nerve Activity ◽  
Pulsatile Pressure ◽  
Rate Frequency

A transfer function from baroreceptor pressure input to sympathetic nerve activity (SNA) shows derivative characteristics in the frequency range below 0.8 Hz in rabbits. These derivative characteristics contribute to a quick and stable arterial pressure (AP) regulation. However, if the derivative characteristics hold up to heart rate frequency, the pulsatile pressure input will yield a markedly augmented SNA signal. Such a signal would saturate the baroreflex signal transduction, thereby disabling the baroreflex regulation of AP. We hypothesized that the transfer gain at heart rate frequency would be much smaller than that predicted from extrapolating the derivative characteristics. In anesthetized rabbits ( n = 6), we estimated the neural arc transfer function in the frequency range up to 10 Hz. The transfer gain was lost at a rate of −20 dB/decade when the input frequency exceeded 0.8 Hz. A numerical simulation indicated that the high-cut characteristics above 0.8 Hz were effective to attenuate the pulsatile signal and preserve the open-loop gain when the baroreflex dynamic range was finite.

Estimation of open-loop gain of canine arterial pressure control system by a new method

1981 ◽  
Vol 240 (6) ◽  
pp. H832-H836 ◽  
Author(s):  
H. Hosomi ◽  
K. Yokoyama
Keyword(s):  
Control System ◽  
Arterial Pressure ◽  
Pressure Change ◽  
Pressure Control ◽  
Systemic Arterial Pressure ◽  
Open Loop ◽  
Loop Gain ◽  
Reflex Gain ◽  
Pressure Control System ◽  
Arterial Pressure Control System

We developed a method to estimate an overall open-loop gain of the arterial pressure control system without surgically opening the reflex loop. Dogs anesthetized by intravenous injection of Nembutal (35 mg/kg body wt) were bled by 2 ml/kg body wt within 2-3 s through a catheter inserted into the abdominal aorta. Arterial pressure change after the quick hemorrhage was monitored via a catheter placed in the aortic arch for more than 2 min. The overall open-loop gain of the lumped arterial pressure control system was assessed as (delta API/delta APs)-1, where delta API is the immediate fall and delta APs the steady-state fall in mean arterial pressure obtained by a filter with a 2-s time constant. The advantage of this method is that the overall open-loop gain can be estimated under the closed-loop condition in which the baroreceptor reflexes operate naturally around the existing range of systemic arterial pressure. This enables one to study time-varying characteristics of the reflex gain. The disadvantage is that the substantial constituents of the lumped reflex system remain to be confirmed.

Baroreflex open-loop gain and arterial pressure compensation in hemorrhagic hypotension

1983 ◽  
Vol 245 (1) ◽  
pp. H54-H59 ◽  
Author(s):  
H. I. Chen ◽  
V. S. Bishop
Keyword(s):  
Arterial Pressure ◽  
Closed Loop ◽  
Control Level ◽  
Systemic Arterial Pressure ◽  
Open Loop ◽  
Loop Gain ◽  
Hemorrhagic Hypotension ◽  
Carotid Baroreceptor ◽  
Loop Condition ◽  
Pressure Compensation

The loop gain (G) of the carotid baroreceptor was determined using open- and closed-loop approach in anesthetized rabbits after aortic denervation and vagotomy. The open-loop relationship between the intrasinus pressure (ISP) and systemic arterial pressure (SAP) was nonlinear. The slope (delta SAP/delta ISP) or G was maximal (about 1.5) near the control arterial pressure and decreased toward the saturation pressures. We examined how this nonlinearity relates to the arterial pressure compensation following hemorrhage. Because the baroreflex attenuation of the posthemorrhagic hypotension depends on the SAP responses to an input perturbation, we first demonstrated that the open-loop responses in SAP to a specific delta ISP was not altered during various amounts of hemorrhage, despite different operating range for the responses. In the open-loop condition when ISP was fixed at the control level, hemorrhage of 10, 20, and 30 ml produced a SAP disturbance (D) of 23.3, 43.5, and 62.4 mmHg, respectively. The figures were minimized to 9.8, 19.8, and 34.4 mmHg (D'), respectively through the baroreflex compensation in the closed-loop condition. The calculated G (D/D' - 1) from the closed-loop data were 1.38, 1.20, and 0.82 for 10, 20, and 30 ml hemorrhage. For a given input signal (delta ISP = D'), the values of G were essentially the same as those obtained from the open-loop ISP-SAP curve. The G values decreased as the degree of hemorrhagic hypotension increased, being in agreement with the sigmoid characteristics of the nonlinear ISP-SAP curve.

Exaggerated pressor response to blood flow restriction resistance exercise is associated with a muscle metaboreflex-induced increase in blood pressure in young, healthy humans

2020 ◽  
Author(s):  
Amane Hori ◽  
Daisuke Hasegawa ◽  
Kenichi Suijo ◽  
Keita Nishigaki ◽  
Koji Ishida ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Blood Pressure Response ◽  
Pressure Response ◽  
Blood Flow Restriction ◽  
Post Exercise ◽  
Muscle Metaboreflex ◽  
Flow Restriction ◽  
Muscle Ischemia ◽  
Exercise Muscle

Some researchers are concerned that exercise training with the blood flow restriction (BFR) technique induces an exaggeration in blood pressure response and potentiates adverse cardiovascular events. In the present study, we demonstrate that the blood pressure response to arm-curl exercise was intensified by the BFR technique, and the degree of intensification was associated with a blood pressure response to post-exercise muscle ischemia of the elbow flexors, which elicit a muscle metaboreflex. Novelty bullet Blood flow restriction technique intensifies blood pressure response to exercise, which was associated with a blood pressure response in post-exercise muscle ischemia-induced muscle metaboreflex.

scholarly journals Jiu-jitsu match elevates myocardial work and causes post-exercise hypotension in master category athletes

2020 ◽  
Vol 19 (3) ◽  
pp. 224
Author(s):  
Tharciano Luiz Teixeira Braga Da Silva ◽  
André Luiz Silva Santos ◽  
Thincia Luandes Mota Barreto ◽  
Fabricio Nunes Macedo ◽  
Vitor Ulisses De Melo ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Martial Arts ◽  
Acute Effects ◽  
Double Product ◽  
Post Exercise ◽  
Before And After ◽  
Baseline Values ◽  
Cardiovascular Variables ◽  
Post Exercise Hypotension

Jiu-jitsu is a sport that involves different techniques to lead the opponent to submission, combats are characterized by intermittent efforts with changes in important cardiovascular variables. Thus, the aim was to evaluate the acute effects of a simulated jiu-jitsu match on blood pressure (BP) and the double product (DP) of fighters in the master category. The heart rate (HR), BP, and DP of six experienced fighters were measured, before and after the protocol. The combat consisted of four six-minute sessions with intervals of three minutes for recovery and measurement of the variables. Measurements were taken every 15 minutes, after the end of the fight. An increase in systolic (SBP) and mean BP (MAP) was observed after the last session. After 30 minutes, there was a decrease in MAP and SBP, until the end of the protocol. Diastolic BP (DBP) decreased after 30 minutes, returning to baseline after 45 minutes post-combat. HR remained high until 30 minutes of recovery. Despite the increase greater than 280% of the DP, verified immediately after the fight, 15 minutes of recovery was sufficient for this index to return to baseline values. The study shows that a jiu-jitsu match causes a significant increase in SBP and MAP, HR and PD with subsequent arterial hypotension.Keywords: cardiovascular physiological phenomena, blood pressure, martial arts.

Rabbit carotid sinus reflex under pentobarbital, urethan, and chloralose anesthesia

1984 ◽  
Vol 246 (5) ◽  
pp. H696-H701 ◽  
Author(s):  
N. Ishikawa ◽  
C. H. Kallman ◽  
K. Sagawa
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Carotid Sinus ◽  
Logistic Function ◽  
Systemic Arterial Pressure ◽  
Open Loop ◽  
Specific Effects ◽  
Reflex Control ◽  
Alpha Chloralose ◽  
Sinus Pressure

To determine the effects of different anesthesias on the performance of the arterial baro-reflex, the open-loop characteristic of the carotid sinus reflex was analyzed in 24 rabbits under anesthesia with pentobarbital (30 mg/kg), urethan (800 mg/kg), alpha-chloralose (80 mg/kg), or a mixture of alpha-chloralose (40 mg/kg) and urethan (0.4 g/kg). For each rabbit and anesthesia, mean systemic arterial pressure and heart rate were measured as carotid sinus pressure was changed in 10-mmHg steps between 40 and 150 mmHg. This set of measurements was repeated four times at 1-h intervals. A logistic function curve was fitted to the carotid sinus pressure-arterial pressure relationship. The parameters of this curve were then analyzed to delineate the specific effects of the anesthesias on the relationship. The main finding was that the response range and the slope parameters under alpha-chloralose anesthesia were significantly smaller than those obtained under the other anesthesias. Propylene glycol, used as the solvent for chloralose, did not affect the reflex control of arterial pressure or heart rate. The reflex under chloralose-urethan anesthesia showed characteristics similar to those under urethan anesthesia. We conclude that although alpha-chloralose has traditionally been used in the dog to obtain strong reflex responses, it weakens the reflex control of arterial pressure in the rabbit.

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