Cardiac sympathetic afferent stimulation impairs baroreflex control of renal sympathetic nerve activity in rats

Lie Gao, Zhen Zhu, Irving H. Zucker, Wei Wang

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

It is well known that cardiac sympathetic afferent reflexes contribute to increases in sympathetic outflow and that sympathetic activity can antagonize arterial baroreflex function. In this study, we tested the hypothesis that in normal rats, chemical and electrical stimulation of cardiac sympathetic afferents results in a decrease in the arterial baroreflex function by increasing sympathetic nerve activity. Under α-chloralose (40 mg/kg) and urethane (800 mg/kg ip) anesthesia, renal sympathetic nerve activity, mean arterial pressure, and heart rate were recorded. The arterial baroreceptor reflex was evaluated by infusion of nitroglycerin (25 μg iv) and phenylephrine (10 μg iv). Left ventricular epicardial application of capsaicin (0.4 μg in 2 μl) blunted arterial baroreflex function by 46% (maximum slope 3.5 ± 0.3 to 1.9 ± 0.2%/mmHg, P < 0.01). When the central end of the left cardiac sympathetic nerve was electrically stimulated (7 V, 1 ms, 20 Hz), the sensitivity of the arterial baroreflex was similarly decreased by 42% (maximum slope 3.2 ± 0.3 to 1.9 ± 0.4%/mmHg; P < 0.05). Pretreatment with intracerebroventricular injection of losartan (500 nmol in 1 μl of artificial cerebrospinal fluid) completely prevented the impairment of arterial baroreflex function induced by electrical stimulation of the central end of the left cardiac sympathetic nerve (maximum slope 3.6 ± 0.4 to 3.1 ± 0.5%/mmHg). These results suggest that the both chemical and electrical stimulation of the cardiac sympathetic afferents reduces arterial baroreflex sensitivity and the impairment of arterial baroreflex function induced by cardiac sympathetic afferent stimulation is mediated by central angiotensin type 1 receptors.

Original languageEnglish (US)
Pages (from-to)H1706-H1711
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume286
Issue number5 55-5
DOIs
StatePublished - May 2004

Keywords

  • Angiotensin type 1 receptor

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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