Effects of aging on cardiac autonomic control in female rats – role of physical training

We investigated in young (10 wks old; n=20) and aged rats (70 wks old; n=20) the effects of physical training on cardiac autonomic control through two different methods; double autonomic blockade of heart rate (HR) by intravenous injections of methylatropine and propranolol; and heart rate variability (HRV) by spectral analysis. Each group was divided into two subgroups; sedentary and trained by swimming (10 wks). Young sedentary rats showed a vagal predominance on the basal HR control, whereas aged rats showed a sympathetic predominance. Physical training increased vagal predominance on the basal HR control in young rats and leaded to an inversion of predominance in aged rats. HRV analysis showed that young and aged rats, subjected or not to physical training, have equal power (normalized units) in low (LF; 0.25 – 0.75 Hz) and high (HF; 0.75 – 2.5 Hz) frequency bands. However, physical training decreased LF power and augmented HF power, suggestion a reduction in sympathetic modulation and an increase in vagal modulation, correspondingly. In conclusion, aging effects are observed when cardiac autonomic control is examined by means of pharmacologic autonomic blockade, but are not observed when evaluated by HRV analysis. Nevertheless, positive physical training effects over cardiac autonomic control are observed in both methods (i.e. pharmacologic autonomic blockade and HRV analysis). Supported by: FAPESP; CAPES