Intrinsic Rate and Cholinergic Sensitivity of Isolated Atria from Trained and Sedentary Rats

Bolter, Chris P.; Hughson, Richard L.; Critz, Jerry B.

doi:10.3181/00379727-144-37592

Cited by 39 publications

(21 citation statements)

References 3 publications

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“…In normal male rats and humans, the reduction in IHR (pacemaker mediated) after exercise training seems to be the causal mechanism of the resting bradycardia (4,23,25). Studies have demonstrated that sympathetic and/or parasympathetic inputs were reduced in trained normotensive male rats or humans (4,5,23,27,28).…”

Section: Discussionmentioning

confidence: 99%

Tonic and reflex cardiovascular autonomic control in trained-female rats

Sanches

Sartori

Jorge

et al. 2009

Braz J Med Biol Res

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The effects of exercise training on cardiovascular and autonomic functions were investigated in female rats. After an aerobic exercise training period (treadmill: 5 days/week for 8 weeks), conscious female Wistar (2 to 3 months) sedentary (S, N = 7) or trained rats (T, N = 7) were cannulated for direct arterial pressure (AP) recording in the non-ovulatory phases. Vagal (VT) and sympathetic tonus (ST) were evaluated by vagal (atropine) and sympathetic (propranolol) blockade. Baroreflex sensitivity was evaluated by the heart rate responses induced by AP changes. Cardiopulmonary reflex was measured by the bradycardic and hypotensive responses to serotonin. Resting bradycardia was observed in T (332 ± 7 bpm) compared with S animals (357 ± 10 bpm), whereas AP did not differ between groups. T animals exhibited depressed VT and ST (32 ± 7 and 15 ± 4 bpm) compared to S animals (55 ± 5 and 39 ± 10 bpm). The baroreflex and cardiopulmonary bradycardic responses were lower in T (-1.01 ± 0.27 bpm/mmHg and -17 ± 6 bpm) than in the S group (-1.47 ± 0.3 bpm/mmHg and -41 ± 9 bpm). Significant correlations were observed between VT and baroreflex (r = -0.72) and cardiopulmonary (r = -0.76) bradycardic responses. These data show that exercise training in healthy female rats induced resting bradycardia that was probably due to a reduced cardiac ST. Additionally, trained female rats presented attenuated bradycardic responses to baro- and cardiopulmonary receptor stimulation that were associated, at least in part, with exercise training-induced cardiac vagal reduction

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Section: Discussionmentioning

confidence: 99%

Tonic and reflex cardiovascular autonomic control in trained-female rats

Sanches

Sartori

Jorge

et al. 2009

Braz J Med Biol Res

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“…Therefore, the cardiac autonomic control seems to be influenced by either training mode or season, a fact that represents an interesting topic for future investigations. Indeed, recent studies have demonstrated that vagal improvement is associated with lower adverse cardiac events such as, lower cardiac arrhythmias (9,26). Conversely, cardiac sympathetic predominance may be hazardous to the cardiovascular system since it triggers arrhythmias (27,28).…”

Section: Heart Rate Adaptationsmentioning

confidence: 99%

“…Other studies investigating the sympatho-vagal balance by spectral analysis have shown increased cardiac vagal tone in exercise-trained humans (8). Alternatively, reduction in intrinsic heart rate (IHR) in exercise-trained rats (9) and exercise-trained humans (10), and more recently longer atrio-ventricular conduction time (11) have led some investigators to attribute resting bradycardia to intrinsic cardiac alteration. These contrasting results might be due to the methodology used to analyze the cardiac autonomic balance, the species studied, and probably to the different training regimens and modes applied.…”

Section: Introductionmentioning

confidence: 99%

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Swimming training increases cardiac vagal activity and induces cardiac hypertrophy in rats

Medeiros

Oliveira

Gianolla

et al. 2004

Braz J Med Biol Res

120

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The effect of swimming training (ST) on vagal and sympathetic cardiac effects was investigated in sedentary (S, N = 12) and trained (T, N = 12) male Wistar rats (200-220 g). ST consisted of 60-min swimming sessions 5 days/week for 8 weeks, with a 5% body weight load attached to the tail. The effect of the autonomic nervous system in generating training-induced resting bradycardia (RB) was examined indirectly after cardiac muscarinic and adrenergic receptor blockade. Cardiac hypertrophy was evaluated by cardiac weight and myocyte morphometry. Plasma catecholamine concentrations and citrate synthase activity in soleus muscle were also determined in both groups. Resting heart rate was significantly reduced in T rats (355 ± 16 vs 330 ± 20 bpm). RB was associated with a significantly increased cardiac vagal effect in T rats (103 ± 25 vs 158 ± 40 bpm), since the sympathetic cardiac effect and intrinsic heart rate were similar for the two groups. Likewise, no significant difference was observed for plasma catecholamine concentrations between S and T rats. In T rats, left ventricle weight (13%) and myocyte dimension (21%) were significantly increased, suggesting cardiac hypertrophy. Skeletal muscle citrate synthase activity was significantly increased by 52% in T rats, indicating endurance conditioning. These data suggest that RB induced by ST is mainly mediated parasympathetically and differs from other training modes, like running, that seems to mainly decrease intrinsic heart rate in rats. The increased cardiac vagal activity associated with ST is of clinical relevance, since both are related to increased life expectancy and prevention of cardiac events. Correspondence

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“…A reduction in the intrinsic atrial rate of endurance trained animals has been reported before (Bolter et al, 1973;Hughson et al, 1977). However, the lower intrinsic atrial rates of the sprint-trained animals surprised us.…”

Section: Discussionmentioning

confidence: 66%

Intrinsic Rates and Adrenergic Responses of Atria From Rats on Sprinting, Endurance and Walking Exercise Programmes

Bolter

1986

Aust J Exp Biol Med

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Summary. The effects of three different physical training programmes on the control of sinoatrial rate in the young male rat were investigated. After training for 8 weeks, 5 d/week, the intrinsic rate and chronotropic response to cumulatively applied norepinephrine (NEp) were examined using isolated atrial preparations. Preparations from animals trained by walking for 60 min/d at 16-1 m/min possessed the same intrinsic atrial rate as sedentary controls, while preparations from an endurance-trained group running for 60 min at 32-2 m/min at 15% grade, and from a sprint-trained group running 50, 10-s efforts at 80-5 m/min, 15% grade with a 30-s rest interval, possessed lower intrinsic atrial rates. Atrial preparations from all groups demonstrated similar maximum rates after application of NEp. For all groups there was no statistically significant difference between the ECJQ values for the chronotropic effect of NEp. Training induced a modification in intrinsic atrial rate without influencing NEp chronotropic responses.

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Intrinsic Rate and Cholinergic Sensitivity of Isolated Atria from Trained and Sedentary Rats

Cited by 39 publications

References 3 publications

Tonic and reflex cardiovascular autonomic control in trained-female rats

Tonic and reflex cardiovascular autonomic control in trained-female rats

Swimming training increases cardiac vagal activity and induces cardiac hypertrophy in rats

Intrinsic Rates and Adrenergic Responses of Atria From Rats on Sprinting, Endurance and Walking Exercise Programmes

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