Direct and vagally mediated chronotropic effects of morphine studied by selective perfusion of the sinus node of awake dogs

Academic Article


  • Two milliliters of a morphine sulfate solution (1 mg/ml) perfused selectively into the sinus node artery of five trained unanesthetized dogs caused an immediate brief sinus tachycardia followed by a delayed but prolonged sinus bradycardia. Beta receptor blockade was achieved by selective perfusion of propranolol hydrochloride solution (10μg/ml) into the sinus node artery and did not prevent the initial sinus tachycardia. Selective perfusion of the sinus node with atropine sulfate solution (1μg/ml), however, did prevent morphine from causing further sinus rate increase. The immediate positive chronotropic action of morphine was thus attributable to a peripherally located vagolytic action. The exact opposite was true with regard to the delayed bradycardia; it was due to a centrally mediated generalized increase in vagal tone regularly elicited by morphine.
  • Published In

  • Chest  Journal
  • Digital Object Identifier (doi)

    Author List

  • Urthaler F; Isobe JH; James TN
  • Start Page

  • 222
  • End Page

  • 228
  • Volume

  • 68
  • Issue

  • 2