Influence of cardiac innervation on intrinsic heart rate in dogs

Intrinsic heart rate is defined as the rate at which the heart beats when all cardiac neural and hormonal inputs are removed. We determined the effect of prevailing autonomic innervation of the heart on the intrinsic heart rate in chronically maintained, sedated, normally innervated dogs (n = 14), and in 14 other dogs that had previously (greater than 12 day) undergone complete surgical cardiac denervation. Intrinsic rate was determined in both groups using the following two procedures: 1) pharmacological effector blockade; and 2) pharmacological ganglionic blockade. The intrinsic rate determined by effector blockade was 142.9 +/- 7.2 (SE) beats/min in the dogs with intact cardiac innervation. When the same treatment was given after total surgical cardiac denervation, intrinsic rate was 97.9 +/- 4.8 beats/min. Intrinsic heart rate was significantly (P less than 0.05) lower in surgically denervated dogs. Ganglionic blockade in surgically denervated animals yielded an intrinsic rate of 90.0 +/- 8.5 beats/min, which was again significantly lower than the corresponding value of 128.4 +/- 5.5 beats/min in normal dogs. There was no difference in the intrinsic heart rate as determined by effector vs. ganglionic blockade in either group of dogs. An additional six dogs were subjected to selective surgical sinoatrial nodal parasympathectomy; their intrinsic rate (effector blockade) in the conscious state was 115.8 +/- 4.3 beats/min; this was significantly lower than the corresponding value for normal dogs and significantly greater than in dogs subject to total surgical cardiac denervation. The lower rate observed in the totally denervated and selectively denervated dogs after effector and/or ganglionic blockades implies that intrinsic heart rate depends on the level or nature of prevailing autonomic activity.

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Decreased maximal heart rate with aging is related to reduced β-adrenergic responsiveness but is largely explained by a reduction in intrinsic heart rate

Journal of Applied Physiology ◽

10.1152/japplphysiol.90401.2008 ◽

2008 ◽

Vol 105 (1) ◽

pp. 24-29 ◽

Cited By ~ 71

Author(s):

Demetra D. Christou ◽

Douglas R. Seals

Keyword(s):

Heart Rate ◽

Maximal Oxygen Consumption ◽

Older Men ◽

Exercise Heart Rate ◽

Maximal Heart Rate ◽

Adrenergic Stimulation ◽

Ganglionic Blockade ◽

Intrinsic Heart Rate ◽

Age Related ◽

Aerobic Exercise Capacity

A decrease in maximal exercise heart rate (HRmax) is a key contributor to reductions in aerobic exercise capacity with aging. However, the mechanisms involved are incompletely understood. We sought to gain insight into the respective roles of intrinsic heart rate (HRint) and chronotropic β-adrenergic responsiveness in the reductions in HRmax with aging in healthy adults. HRmax (Balke treadmill protocol to exhaustion), HRint (HR during acute ganglionic blockade with intravenous trimethaphan), and chronotropic β-adrenergic responsiveness (increase in HR with incremental intravenous infusion of isoproterenol during ganglionic blockade) were determined in 15 older (65 ± 5 yr) and 15 young (25 ± 4 yr) healthy men. In the older men, HRmax was lower (162 ± 9 vs. 191 ± 11 beats/min, P < 0.0001) and was associated with a lower HRint (58 ± 7 vs. 83 ± 9 beats/min, P < 0.0001) and chronotropic β-adrenergic responsiveness (0.094 ± 0.036 vs. 0.154 ± 0.045 ΔHR/[isoproterenol]: P < 0.0001). Both HRint ( r = 0.87, P < 0.0001) and chronotropic β-adrenergic responsiveness ( r = 0.61, P < 0.0001) were positively related to HRmax. Accounting for the effects of HRint and chronotropic β-adrenergic responsiveness reduced the age-related difference in HRmax by 83%, rendering it statistically nonsignificant ( P = 0.2). Maximal oxygen consumption was lower in the older men (34.9 ± 8.1 vs. 48.6 ± 6.7 ml·kg−1·min−1, P < 0.0001) and was positively related to HRmax ( r = 0.62, P < 0.0001), HRint ( r = 0.51, P = 0.002), and chronotropic β-adrenergic responsiveness ( r = 0.47, P = 0.005). Our findings indicate that, together, reductions in HRint and chronotropic responsiveness to β-adrenergic stimulation largely explain decreases in HRmax with aging, with the reduction in HRint playing by far the greatest role.

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Beat-by-beat modulation of AV conduction. II. Autonomic neural mechanisms

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1986.251.6.h1134 ◽

1986 ◽

Vol 251 (6) ◽

pp. H1134-H1142 ◽

Cited By ~ 5

Author(s):

M. R. Warner ◽

J. M. deTarnowsky ◽

C. C. Whitson ◽

J. M. Loeb

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Intrinsic Rate ◽

Conscious State ◽

Neural Mechanisms ◽

Parasympathetic Activity ◽

Atrial Pacing ◽

Rate Dependent ◽

Av Conduction ◽

Electrocardiogram Ecg

We examined the mechanism by which autonomic neural activity associated with respiration and blood pressure modulates atrioventricular (AV) conduction in conscious dogs. Mongrel dogs were anesthetized and instrumented under sterile conditions to record atrial and ventricular electrograms and blood pressure. In the conscious state, electrocardiogram (ECG), respiration, blood pressure, and electrograms were recorded continuously, and heart rate and AV interval were plotted graphically as a function of time. To delineate the role(s) of sympathetic and parasympathetic activity, AV conduction was studied during abrupt and linear changes in heart rate after administration of atropine, propranolol, or both. In the basal state and after propranolol, AV interval oscillated with respiration both in the absence of atrial pacing and at pacing rates 10–100 beats/min above control. Following atropine, oscillations in AV interval associated with respiration were abolished; however, linear and abrupt heart rate increases resulted in AV conduction changes that were associated with fluctuations in blood pressure. In contrast, after both atropine and propranolol, alterations in blood pressure or respiration did not influence AV conduction and rate-dependent prolongation of AV conduction occurred. We conclude that in the basal state, AV conduction is influenced predominately by changes in parasympathetic activity which is the major determinant of respiratory-related AV interval oscillations; after atropine, sympathetic activity produces fluctuations in both AV conduction and blood pressure; and intrinsic rate-dependent properties of the AV node are modulated continually by both divisions of the autonomic nervous system.

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Contribution of neurogenic mechanisms to control of intrinsic heart rate

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1989.256.1.r231 ◽

1989 ◽

Vol 256 (1) ◽

pp. R231-R235 ◽

Cited By ~ 6

Author(s):

B. H. Machado ◽

M. J. Brody

Keyword(s):

Heart Rate ◽

Renal Hypertension ◽

Cardiac Pacemaker ◽

Renin Angiotensin System ◽

Intrinsic Rate ◽

Nucleus Ambiguus ◽

Autonomic Tone ◽

Additional Increase ◽

Humoral Factors ◽

Intrinsic Heart Rate

Altered autonomic tone as well as humoral factors can change the intrinsic rate of the cardiac pacemaker. To study the relationships of neurogenic and humoral factors on intrinsic heart rate (IHR) we used sinoaortic deafferentation (SAD) to increase sympathetic activity, lesion of nucleus ambiguus to reduce central parasympathetic activity, and one-kidney, one-clip (1K1C) renal hypertension to transiently increase the activity of the renin-angiotensin system and the combination of 1K1C hypertension with SAD. In conscious rats, IHR was determined using combined blockade with atropine and propranolol. Rats with 1K1C hypertension (7th day) showed increased mean arterial pressure (MAP), heart rate (HR), and IHR. Rats with SAD (4th day) demonstrated increased MAP and HR, but in contrast, had decreased IHR. Lesion of nucleus ambiguus increased HR and decreased IHR. When 1K1C hypertension was combined with SAD an additional increase in MAP and HR occurred, whereas IHR was reduced compared with renal hypertension alone. These data suggest that IHR is influenced greatly by autonomic tone and that the tachycardia in renal hypertension is linked to increased IHR that is dependent on integrity of the baroreflex.

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The Health Effects of Mercury on the Cardiac Autonomic Activity According to the Heart Rate Variability

Korean Journal of Occupational and Environmental Medicine ◽

10.35371/kjoem.2008.20.4.302 ◽

2008 ◽

Vol 20 (4) ◽

pp. 302 ◽

Cited By ~ 1

Author(s):

Sinye Lim ◽

Min Cheol Choi ◽

Kee Ock Joh ◽

Domyung Paek

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Health Effects ◽

Autonomic Activity ◽

Cardiac Autonomic Activity

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Comparison of autonomic activity between N2 and N3 stages of NREM sleep: evaluation through heart rate variability metrics

Sleep and Biological Rhythms ◽

10.1007/s41105-020-00305-6 ◽

2021 ◽

Author(s):

Erik L. Mateos-Salgado ◽

Fructuoso Ayala-Guerrero

Keyword(s):

Heart Rate ◽

Heart Rate Variability ◽

Nrem Sleep ◽

Autonomic Activity

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Sleep Indices and Cardiac Autonomic Activity Responses during an International Tournament in a Youth National Soccer Team

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18042076 ◽

2021 ◽

Vol 18 (4) ◽

pp. 2076

Author(s):

Pedro Figueiredo ◽

Júlio Costa ◽

Michele Lastella ◽

João Morais ◽

João Brito

Keyword(s):

Heart Rate ◽

Frequency Domain ◽

Sleep Duration ◽

Time Domain ◽

Soccer Players ◽

Autonomic Activity ◽

Male Youth ◽

Youth Soccer ◽

Wrist Actigraphy ◽

Cardiac Autonomic Activity

This study aimed to describe habitual sleep and nocturnal cardiac autonomic activity (CAA), and their relationship with training/match load in male youth soccer players during an international tournament. Eighteen elite male youth soccer players (aged 14.8 ± 0.3 years; mean ± SD) participated in the study. Sleep indices were measured using wrist actigraphy, and heart rate (HR) monitors were used to measure CAA during night-sleep throughout 5 consecutive days. Training and match loads were characterized using the session-rating of perceived exertion (s-RPE). During the five nights 8 to 17 players slept less than <8 h and only one to two players had a sleep efficiency <75%. Players’ sleep duration coefficient of variation (CV) ranged between 4 and 17%. Nocturnal heart rate variability (HRV) indices for the time-domain analyses ranged from 3.8 (95% confidence interval, 3.6; 4.0) to 4.1 ln[ms] (3.9; 4.3) and for the frequency-domain analyses ranged from 5.9 (5.6; 6.5) to 6.6 (6.3; 7.4). Time-domain HRV CV ranged from 3 to 10% and frequency-domain HRV ranged from 2 to 12%. A moderate within-subjects correlation was found between s-RPE and sleep duration [r = −0.41 (−0.62; −0.14); p = 0.003]. The present findings suggest that youth soccer players slept less than the recommended during the international tournament, and sleep duration was negatively associated with training/match load.

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