Effects of NO on baroreflex control of heart rate and renal nerve activity in conscious rabbits

Jun Li Liu, Hiroshi Murakami, Irving H. Zucker

Research output: Contribution to journalArticle

109 Scopus citations

Abstract

Recent data suggest that nitric oxide (NO) plays a role in the modulation of sympathetic nerve activity and baroreflex sensitivity. Most of these studies have been carried out in anesthetized preparations, and little if any comparison has been made on the relative role of NO on the baroreflex control of heart rate and sympathetic nerve activity. In the present studies, the effect of the NO synthase inhibitor N(G)-nitro-L-arginine (L-NNA) on the baroreflex control of heart rate (HR) and renal sympathetic nerve activity (RSNA) were investigated in conscious, instrumented rabbits. Intravenous bolus injections of 13 mg/kg of L-NNA decreased baseline HR (from 205.0 ± 6.0 to 145.5 ± 8.2 beats/min; P < 0.05) without significant changes in mean arterial pressure (MAP) and RSNA. L-NNA significantly reduced the lower plateau of the HR-MAP curves and increased the sensitivities of baroreflex control of HR and RSNA. L-Arginine (600 mg/kg iv) but not D-arginine reversed the above effects. The effects of L-NNA on baseline HR were not completely blocked by metoprolol (2 mg/kg) or by atropine (0.2 mg/kg). After pretreatment with metoprolol, baroreflex sensitivity was reduced and L-NNA increased baroreflex sensitivity back to the control level. After pretreatment with atropine, L-NNA still reduced the lower plateau but did not significantly affect baroreflex sensitivity. L-NNA increased the HR responses but not the RSNA response to electrical stimulation of the aortic nerve in chloralose-anesthetized, sinoaortic-denervated (SAD) rabbits. LNNA had no effect on the HR response to right vagal stimulation. In both conscious intact and SAD rabbits, L-NNA did not increase baseline RSNA. These results suggest that endogenous NO decreases baroreflex control of HR and RSNA. Both sympathetic and parasympathetic components play a role in the effects of NO on the baroreflex control of HR. The effects of NO in the central nervous system play a more important role in the baroreflex control of HR than of RSNA.

Original languageEnglish (US)
Pages (from-to)R1361-R1370
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume270
Issue number6 39-6
StatePublished - Jun 1 1996

Keywords

  • autonomic tone
  • blood pressure
  • nitric oxide
  • vagus

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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