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

Abstract

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

Exercise changes regional vascular control by commissural NTS in spontaneously hypertensive rats

“…Exercise training for 8 wk or more increases the activity of citrate synthase (29,30,32). Indeed, our exercise protocol was not enough to produce the same metabolic muscular changes observed in trained animals.…”

“…This effect has been also attributed to causing the decrease in the cardiac output in low-intensity exercise-trained SHR and, consequently, for reducing the hypertension (46). Postexercise hypotension may persist for more than 12 h (16, 19), and it has been reported that arterial baroreceptor reflex is required for this reduction in arterial pressure (7), but all of the mechanisms underlying this effect are not fully understood.Most of the previous studies have shown that exercise training reduces hypertension, and the peripheral mechanisms involved to produce this effect have been largely investigated in humans and animals (3,7,12,13,17,19,27,30,39,44). On the other hand, there are few studies showing the possible central mechanisms underlying the cardiovascular changes evoked by exercise training in animals.…”

“…Most of the previous studies have shown that exercise training reduces hypertension, and the peripheral mechanisms involved to produce this effect have been largely investigated in humans and animals (3,7,12,13,17,19,27,30,39,44). On the other hand, there are few studies showing the possible central mechanisms underlying the cardiovascular changes evoked by exercise training in animals.…”

Eccentric and concentric cardiac hypertrophy induced by exercise training: microRNAs and molecular determinants

“…With regard to the cardiovascular effects, resting bradycardia has been considered to be the hallmark of aerobic exercise training adaptation (12,19,22). The mechanisms underlying the resting bradycardia are strongly dependent on the exercise training mode.…”

Study of Wistar Rats Heart at Different Stages in the Evolutionary Cycle

“…Nor does it describe in detail the methodology for obtaining these hearts (Medeiros et al, 2000). Medeiros et al (2004) described the ratio of heart weight / body weight in 12 male albino Wistar, weighing 200-220 g and 2.82 ± 0.16 mg/g, where the hearts were removed and the dissection of the thoracic cavity was described only as obtaining hearts after removal of non-cardiac tissues. Therefore, this article proposes to make a detailed study of the heart weight of these animals in relation to body weight than the minimum and maximum diameters of the body so that future researchers can obtain more detailed information.…”