Thromboxane A2 mimetic evokes a bradycardia mediated by stimulation of cardiac vagal afferent nerves

Michael J. Wacker, Roya N. Tehrani, Rory L. Smoot, James A. Orr

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

Injections of the thromboxane A2 mimetic U-46619 (10 and 20 μg) into the left atrium of anesthetized rabbits evoked decreases in heart rate (HR) and arterial blood pressure (ABP) followed by an increase in ABP. Bilateral, cervical vagotomy abolished the U-46619-induced bradycardia and attenuated the hypotension. Injections of U-46619 into the ascending aorta did not evoke the bradycardia and hypotension but did cause arterial hypertension. To further define the origin of the vagal reflex, recordings of nerve impulses were made from 11 chemosensitive cardiac vagal afferent nerves. Impulse frequency increased in all 11 fibers in response to left atrial injections of phenylbiguanide (20-30 μg) and U-46619 (5-10 μg). Onset time of nerve activity induced by U-46619 correlated with the onset time of bradycardia. We conclude that U-46619 injections into the left heart elicit decreases in HR and ABP via a vagal reflex that originates from the heart similar to the coronary chemoreflex described for other agents.

Original languageEnglish (US)
Pages (from-to)H482-H490
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume282
Issue number2 51-2
DOIs
StatePublished - Jan 1 2002

Keywords

  • Anesthetized rabbits
  • Coronary chemoreflex
  • Phenylbiguanide
  • Prostaglandins

ASJC Scopus subject areas

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

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