Effects of digitoxin treatment on reflex cardiovascular control in rats with heart failure (1132.2)

Abstract

There is evidence that digitalis promote changes in the autonomic and reflex control of the cardiovascular system and enhances survival in rats with Heart Failure (HF). The major aim of the present study was to evaluate the effects of digitoxin treatment on basal renal sympathetic nerve activity (rSNA) and on the reflex control of the cardiovascular system by the arterial baroreceptors and cardiopulmonary reflex in HF rats. Male Wistar rats (±200g) were divided into two experimental groups: HF and HF treated with digitoxin in the diet for 60 days (1mg/Kg/day) (HF+DIG). A significant increase in rSNA were found in HF (190 ± 29pps; N= 5) compared to control rats (98 ± 14pps, N=5). Digitoxin treatment leads to a significant decrease and normalizes rSNA in HF+DIG rats (98 ± 14pps, N= 7). The baroreflex sensitivity for the control of rSNA was significantly decreased by treatment (slope: ‐0.69 ± 0.10pps/mmHg, N= 7) when compared to HF group (slope: ‐2.66 ± 0.12pps/mmHg, N= 5). A similar result was found for the cardiopulmonary reflex, digitoxin reduced the fall in heart rate (HF: 180 ± 7bpm, N=8; HF+DIG: ‐126 ± 14bpm, N=9) in response to acute phenylbiguanide administration. Altogether the results demonstrate that the fall in rSNA in response to digitoxin in HF rats is not related to improvement in the reflex control of the cardiovascular system. Central actions of digitoxin may explain the sympathoinhibitory effects of digitalis.Grant Funding Source: CAPES, CNPq and FAPESP (2009/54225‐8)