Effects of physical exercise on baroreflex sensitivity and renal sympathetic nerve activity in chronic nicotine-treated rats.

BACKGROUND Chronic nicotine exposure may increase cardiovascular risk by impairing the autonomic function. Besides, physical exercise (PE) has shown to improve cardiovascular health. We thus aimed to investigate the effects of PE on baroreflex sensitivity (BRS), heart rate variability (HRV), and sympathetic nerve activity (SNA) in chronically-nicotine exposed rats. METHODS Male Wistar rats were assigned to four independent groups: Control (treated with saline solution), Control + Exercise (saline + PE), Nicotine (treated with Nicotine), and Nicotine + Exercise (Nicotine + PE). Nicotine (1 mg · kg-1) was administered daily for 28 consecutive days. PE consisted of running exercise (60 - 70% of maximal aerobic capacity) for 45 minutes, five days per week, for four weeks. At the end of the protocol, cardiac BRS, HRV, renal SNA (rSNA), and renal BRS were assessed. RESULTS Nicotine treatment decreased absolute values of HRV indexes, increased LF/HF, reduced the bradycardic and sympathoinhibitory baroreceptor reflex responses, and reduced the rSNA. PE effectively restored time-domain HRV indexes, the bradycardic and sympathoinhibitory reflex responses, and the rSNA in chronic nicotine treated rats. CONCLUSION PE was effective in preventing the deterioration of time-domain parameters of HRV, arterial baroreceptor dysfunction, and the rSNA after nicotine treatment.