Electrical stimulation of cardiac sympathetic nerves elicited significantly greater reflex renal sympathetic nerve activity in dogs with heart failure compared to sham controls (21.4% vs 9.8%; P<0.05).
Does heart failure enhance the central gain of the cardiac sympathetic afferent reflex in dogs, and is it mediated by central angiotensin II?
The central gain of the cardiac sympathetic afferent reflex is enhanced in dogs with heart failure, a response significantly mediated by central angiotensin II.
Tasa de eventos absoluta: 21.4% vs 9.8%
valor p: p=< 0.05
Previous studies from our laboratory have shown that the cardiac sympathetic afferent reflex is enhanced in dogs with experimental heart failure. The aim of the present study was to determine if the central gain of the cardiac sympathetic afferent reflex was also enhanced in dogs with heart failure. Fifteen dogs with pacing-induced heart failure were used in this study. Seventeen sham-operated dogs served as control. At the time of the acute experiment the dogs were anesthetized with alpha-chloralose. Arterial blood pressure, heart rate, and renal sympathetic nerve activity were recorded. After sinoaortic denervation and cervical vagotomy, a thoracotomy was performed in the second intercostal space. The left stellate ganglion was identified, and the left cardiac sympathetic nerves were cut. The central end of the left cardiac sympathetic nerves was placed on bipolar stimulating electrodes. The renal sympathetic nerve activity responses to electrical stimulation (30 Hz, 1 ms with varying voltages from 1 to 10 V; or 10 V, 1 ms with varying frequencies from 1 to 30 Hz) of the afferent cardiac sympathetic nerves were compared between sham and heart failure groups. Reflex renal sympathetic nerve activity responses to stimulation of the cardiac sympathetic nerves were significantly greater in the heart failure group compared with that in the sham group (21.4 +/- 3.2 vs. 9.8 +/- 2.9% at 10 V, 30 Hz and 27.7 +/- 4.5 vs. 9.9 +/- 3.4% at 30 Hz, 10 V, heart failure vs. sham group, respectively; for both relationships, P < 0.05). This enhanced central gain of the cardiac sympathetic afferent reflex in the heart failure group was significantly attenuated after intravenous and cerebroventricular injection of the angiotensin II receptor antagonist losartan (5 mg/kg i.v. and 0.125 mg/kg in 0.1 ml i.c.v.). These data suggest that the central gain of the cardiac sympathetic afferent reflex is enhanced in dogs with heart failure and central angiotensin II plays an important role in this enhanced response.
Ma et al. (Mon,) conducted a other in Heart failure (n=32). Electrical stimulation of afferent cardiac sympathetic nerves vs. Sham-operated controls was evaluated on Reflex renal sympathetic nerve activity response to electrical stimulation (p=< 0.05). Electrical stimulation of cardiac sympathetic nerves elicited significantly greater reflex renal sympathetic nerve activity in dogs with heart failure compared to sham controls (21.4% vs 9.8%; P<0.05).
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