Sympathetic Activity In Heart Research Articles

Exercise training in heart failure: reduction in angiotensin II, sympathetic nerve activity, and baroreflex control

neurohumoral excitation has been considered the hallmark of heart failure. At the humoral level, cardiac dysfunction has been shown to be associated with increased angiotensin II, aldosterone, and vasopressin levels. The clinical implication for such humoral dysregulation is the increase in salt and

The effects of various carbohydrates on sympathetic activity in heart and interscapular brown adipose tissue of the rat

The present studies were undertaken to determine the effect of various carbohydrates on sympathetic nervous system (SNS) activity. Tritiated-norepinephrine (3H-NE) turnover was measured in heart and interscapular brown adipose tissue (IBAT) of rats fed either chow or chow plus 50% caloric supplements of fructose, sucrose, dextrose, or corn starch. Additional studies were performed to examine whether absorption of carbohydrate plays a role in the SNS response, and to determine whether sweet taste in the from of artificial sweeteners may influence SNS activity. After five to ten days on the respective diets, 3H-NE turnover was increased to a similar extent by all carbohydrates tested (from 38% to 160% greater than controls in different studies). Addition of acarbose (which impairs sucrose absorption) to a sucrose-supplemented diet abolished the SNS stimulatory response, whereas cholestyramine (a drug that blocks fat absorption) had no effect. Finally, the addition of saccharin or aspartame to a chow diet failed to alter SNS activity. Thus, caloric supplementation with several carbohydrates, in addition to sucrose, stimulates both cardiac and IBAT SNS activity, absorption of carbohydrate is required for this effect, and noncaloric sugar substitutes do not alter SNS function.

Diet, lighting, and food intake affect norepinephrine turnover in dietary obesity.

The effects of dietary fat content, lighting cycle, and feeding time on norepinephrine turnover in interscapular brown adipose tissue, heart, and pancreas, and on blood 3-hydroxybutyrate, serum glucose, insulin, and corticosterone have been studied in two strains of rats that differ in their susceptibility to dietary obesity. S 5B/Pl rats, which are resistant to dietary obesity, have a more rapid turnover of norepinephrine in interscapular brown adipose tissue and heart and a greater increase in the concentration of norepinephrine in brown fat when eating a high-fat diet than do Osborne-Mendel rats, which are sensitive to fat-induced obesity. Light cycle and feeding schedule are important modulators of sympathetic activity in heart and pancreas but not in brown fat. Rats of the resistant strain also have higher blood 3-hydroxybutyrate concentrations and lower insulin and corticosterone levels than do rats of the susceptible strain. A high-fat diet increases 3-hydroxybutyrate concentrations and reduces insulin levels in both strains. These studies show, in rats eating a high-fat diet, that differences in norepinephrine turnover, particularly in brown adipose tissue, may play an important role in whether dietary obesity develops and in the manifestations of resistance to this phenomenon observed in the S 5B/Pl rat.

Adaptive changes in central and peripheral noradrenergic neurons in rats following chronic exercise

The turnover rate of endogenous 14C-dopamine and 14C-noradrenaline after administration of 14C-tyrosine was studied in brain, heart and spleen of chronically exercised (trained) rats, while the animals were at rest. In the brains of trained animals the half lives of 14C-dopamine and 14C-noradrenaline were unchanged. However, the noradrenaline concentration of the brain was 26% greater in trained animals and so the calculated total amount of noradrenaline turning over per gram of brain tissue per hour was about one-third greater than in brains of untrained control rats. In peripheral organs there was a striking difference between trained and control rats in the half life of 14C-noradrenaline stores. In the hearts of trained rats, the apparent half life of 14C-noradrenaline was 79 h (statistically not significantly different from infinity), compared with 8.1 h in the heart of control rats. In the spleens, the corresponding apparent half lives of 14C-noradrenaline were infinity and 5.5 h, respectively. The results indicate firstly, that some noradrenergic neurons in the brain react to chronic increases in their impulse flow by increasing their stores of transmitter, just as do noradrenergic neurons in the heart and chromaffin cells in the adrenal medulla; secondly that chronically exercised animals display marked Adaptive changes in the functioning of peripheral sympathetic neurons, there being little if any sympathetic activity in heart and spleen during rest; and thirdly, that there is an inverse relationship between the changes in activity in central compared with peripheral noradrenergic neurons as a result of Adaptation to chronic exercise.