Laterza MC, de Matos LD, Trombetta IC, Braga AM, Roveda F, Alves MJ, Krieger EM, Negrão CE, Rondon MU. Heart Institute (InCor), University of São Paulo Medical School, São Paulo, Brazil.Hypertension. 2007 Jun;49(6):1298-306. Epub 2007 Apr 16.
As we have already established, the baroreflex is an important mechanism in cardiovascular control, and exercise is a good way to deal with the hypertension. There is a possibility that arterial baroreflex sensitivity is decreased in individuals who suffer from some cardiovascular diseases, such as hypertension. Based on this possibility, the researchers in this study wanted to find if there was a decreased baroreflex response upon muscle sympathetic nerve activity (MSNA) and blood pressure (BP) and whether these two parameters were related in their changes in response to the exercise.
Using 20 hypertensive individuals who have never been treated for that condition before, as well as 10 normotensive individuals as a control, they made two subgroups of exercise-trained and non-exercised trained individuals. The MSNA was monitored by microneurography, and the BP was monitored both by sphygmomanometer and by a finger photoplethysmography device. Arterial baroreflex responsiveness was measured by infusion of either phenylephrine or sodium nitroprusside into the antecubital vein while monitoring drug effects upon mean BP, MSNA, and heart rate.
In the hypertensive individuals, their BP was significantly higher than in the normotensive individuals, and their MSNA had a higher burst frequency and burst incidence than the normotensive individuals. Baroreflex control of the BP was significantly lower in the hypertensive individuals. At the conclusion of the experiment, the baroreflex control of the exercise trained individuals was more on par with the baroreflex control of the normotensive individuals. Also, the changes in MSNA and changes in BP were significantly correlated in the exercise-trained and non-trained individuals.
Therefore, baroreflex control of MSNA was shown, by this study, to be decreased in hypertensive individuals, and that exercise would produce control that is similar to the level found in normotensive individuals. Also, the study showed a relationship between MSNA activity and BP, but does not establish how they are related.
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