The Effects Of Exercise On The Heart Rate Regulation Of The Parasympathetic Nerves In The Normal And Obese Rats

Objective:To study the effects of different intensity exercise on the heart rate regulation of the parasympathetic nervous system in normal and obese rats, using the rat treadmill model, which evaluates the measurement of fitness and is induced by the high-fat and high sucrose food. The aim is to understand the effect of different intensity exercise on the autonomic nervous system.Methods:40ten-week-old male SD rats were divided into three groups, after having the max running velocity measurement of all the rats. The groups were designated as C, M and H Groups.14rats ran at the mid-intensity as M Group;14rats ran at the high-intensity as H Group and the C Group was maintained as the control.group including12rats.90four-week-old male SD rats were divided into two groups, designated as C Group (12rats) being fed with normal food and F Group (78rats) being fed with high-fat and high sucrose food. After8weeks, the heaviest36rats were chosen from F Group as obese rats and divided into three groups after having the max running velocity measurement. The groups were designated as FC, FM and FH Groups.12rats ran at the mid-intensity as FM Group;12rats ran at the high-intensity as FH Group and the FC Group was maintained as the control group including12rats. After the next8weeks of training, the heart rate of the rats was tested at rest and15min after injecting atropine and/or propranolol; The Elisa and RT-PCR were used to detect the proteins and mRNA expressions of M2receptor, RGS6and Kir3.4.Results:(1)The regulation of heart rate by vagal was reduced by both8weeks mid-intensity exercise and8weeks high-intensity exercise.(2)8weeks mid-intensity exercise increased the expression of M2receptor, but both mid-intensity and high-intensity exercise had no effect on the expression of RGS6and KCNJ5.(3) Both kinds of exercise reduced the mRNA expressions of M2receptor, RGS6and Kir3.4.(4) The heart rate at rest of the rats with8weeks high-fat and high sucrose food were lower than the rats with the normal food.(5)8weeks of high-intensity exercise injured the microstructure of obese rats’heart, but both kinds of exercise had no effect on the heart rate at rest.(6) Both kinds of exercise had no effect on the expression of the M2receptor, RGS6and KCNJ5in the obese rats; but affected the mRNA expression of M2receptor, RGS6and Kir3.4.Conclusions:1)Both8weeks mid-intensity exercise and high-intensity exercise can reduce the heart rate regulations of vagal, but they do not have the same effect on the obesity and the effect does not work by M2receptor, KCNJ5and RGS6;2) Obesity induced by high-fat and high-sucrose food accompanys with the change in the sympathetic-vagal balance; the main effect on the autonomic nervous system is a change from vagal to sympathetic nervous system.3)it seems the heart rate regulation of autonomic nervous system does not relate the intensity of the exercise.