Exercise training improves hypertension-induced autonomic dysfunction without influencing properties of peripheral cardiac vagus nerve

Abstract

We examined the vagal transfer function of autonomic heart rate (HR) control in anesthetized sedentary and exercise-trained Spontaneously Hypertensive Rats (SHR). To this end, male SHR and Wystar-Kyoto (WKY) rats with 48-50weeks of age-old were divided into 4 groups: sedentary (SHR_S, n=12) and trained (SHR_T, n=14) hypertensive rats, sedentary (WKY_S, n=13) and trained (WKY_T, n=13) normotensive rats. The trained groups were submitted to swimming protocol for 9weeks. Blood pressure (BP), HR, HR variability (HRV), BP variability (BPV), baroreflex sensitivity and cardiac tonus were recorded in baseline conditions. Following, electric stimulation of peripheral vagus nerve was performed in anesthetized conditions. Resting bradycardia was observed in SHR_T and WKY_T when compared to their respective sedentary groups (p<0.001). The BP was lower in SHR_T than in SHR_S (p<0.001). The SHR_T and WKY_T rats showed higher baroreflex-mediated tachycardia values when compared to their respective sedentary counterparts (p<0.001). Baroreflex bradycardic response in SHR_T was higher than in SHR_S (p<0.005). The SHR_T and WKY_T rats showed a decreased sympathetic activity in comparison to their respective sedentary groups (p<0.05). The cardiac vagal tonus was higher in SHR_T than in SHR_S (p<0.05). Regarding the dynamic transducer properties of peripheral vagus nerve to the heart no difference was observed among the groups. In conclusion, our results demonstrate that exercise training decreased BP in SHR and improved cardiovascular autonomic balance to the heart without changes in transduction properties of peripheral cardiac vagus nerve.

Keywords: Autonomic dysfunction; Cardiac autonomic control; Exercise training; Hypertension; Vagal efferent nerve.