The influence of vagal afferents on the left ventricular contractile response to intracoronary administration of catecholamines in the conscious dog

K. W. Barron, V. S. Bishop

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18 Citations (Scopus)

Abstract

We studied the effect of vagal afferents on the left ventricular contractile response [LVdP/dt(max)] to administration of sympathomimetic amines into the left circumflex coronary artery in conscious dogs. The positive inotropic effects of bolus administration of epinephrine, norepinephrine, and isoproterenol were greater during bilateral vagal cold block (BVB) than in the control state with the vagi intact (P<0.001). The inotropic potentiation observed with BVB was not due to vagal efferent interruptions, since parasympathetic efferent block with atropine did not potentiate the inotropic effects of intracoronary epinephrine (P>0.05). BVB also potentiated the inotropic effects of constant intracoronary infusion of epinephrine (P<0.01). BVB alone had no significant effect on LVdP/dt(max); however, BVB during constant intracoronary infusion of epinephrine did result in an increase in LVdP/dt(max) (P<0.05). We propose that the potentiation of the inotropic effects during BVB could result from either interruption of a vagal afferent-mediated negative feedback reflex and/or an unmasking of a sympathetic afferent-mediated positive feedback effect induced by BVB. However, the observations that ganglionic blockade also potentiated the contractile effects of epinephrine supports the concept that a negative feedback reflex does attenuate the inotropic effect of catecholamines in the control state. In conclusion, these data suggest that vagal afferents attenuate the positive inotropic effects of intracoronary administration of catecholamines via a cardiocardiac negative feedback reflex which occurs through a vagal afferent inhibition of sympathetic efferent activity back to the left ventricle.

Original languageEnglish
Pages (from-to)159-169
Number of pages11
JournalCirculation Research
Volume49
Issue number1
DOIs
StatePublished - 1 Jan 1981

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Catecholamines
Dogs
Epinephrine
Reflex
Sympathomimetics
Isoproterenol
Heart Ventricles
Coronary Vessels
Norepinephrine

Cite this

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abstract = "We studied the effect of vagal afferents on the left ventricular contractile response [LVdP/dt(max)] to administration of sympathomimetic amines into the left circumflex coronary artery in conscious dogs. The positive inotropic effects of bolus administration of epinephrine, norepinephrine, and isoproterenol were greater during bilateral vagal cold block (BVB) than in the control state with the vagi intact (P<0.001). The inotropic potentiation observed with BVB was not due to vagal efferent interruptions, since parasympathetic efferent block with atropine did not potentiate the inotropic effects of intracoronary epinephrine (P>0.05). BVB also potentiated the inotropic effects of constant intracoronary infusion of epinephrine (P<0.01). BVB alone had no significant effect on LVdP/dt(max); however, BVB during constant intracoronary infusion of epinephrine did result in an increase in LVdP/dt(max) (P<0.05). We propose that the potentiation of the inotropic effects during BVB could result from either interruption of a vagal afferent-mediated negative feedback reflex and/or an unmasking of a sympathetic afferent-mediated positive feedback effect induced by BVB. However, the observations that ganglionic blockade also potentiated the contractile effects of epinephrine supports the concept that a negative feedback reflex does attenuate the inotropic effect of catecholamines in the control state. In conclusion, these data suggest that vagal afferents attenuate the positive inotropic effects of intracoronary administration of catecholamines via a cardiocardiac negative feedback reflex which occurs through a vagal afferent inhibition of sympathetic efferent activity back to the left ventricle.",
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