Ad libidum exercise improves functional sympatholysis in rats with spontaneous hypertension via the nitric oxide signal pathway

Abstract

Objective To explore the effect of exercise on functional sympatholysis in rats modeling spontaneous hypertension and the role of the nitric oxide signal pathway. Methods Thirty Wistar rats with spontaneous hypertension were randomly divided into a sedentary group and an exercise group, each of 15, while another fifteen healthy rats acted as controls. The exercise group performed eight weeks of voluntary wheel running exercise while the other two groups did not. The rats were instrumented to stimulate the lumbar sympathetic chain (at 1 Hz, 2.5 Hz or 5 Hz) to induce vasoconstriction and the triceps surae muscle group was forced to contract by stimulating the tibial nerve electrically. The change in the femoral artery vascular conductance (FAVC) in response to sympathetic stimulation was recorded at rest and during contraction. The functional sympatholysis was calculated as the percentage difference in FAVC (△%FAVC) in response to sympathetic stimulation during muscular contraction and at rest (△%FAVC=%FAVC during contraction-%FAVC at rest). After administration of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME), changes in FAVC were repeatedly determined. Results The average △%FAVC of the sedentary group was significantly lower than that of the control group at all stimulation frequencies, while the average △%FAVC in the exercise group was significantly higher than in the sedentary group. There were no significant differences between the exercise and control groups. After the administration of L-NAME, significant decrease was observed in the average △%FAVCs of the control and exercise groups, but there was no significant change in the sedentary group. Conclusion Voluntary exercise may improve functional sympatholysis in rats with spontaneous hypertension through improving NO-dependent signalling. Key words: Exercise; Hypertension; Functional sympatholysis; Nitric oxide