Autonomic nervous system pulmonary vasoregulation after hypoperfusion in conscious dogs.
We investigated the role of the autonomic nervous system (ANS) in the pulmonary vascular response to increasing cardiac index after a period of hypoperfusion (defined as reperfusion) in conscious dogs. Base-line and reperfusion pulmonary vascular pressure-cardiac index (P/Q) plots were generated by stepwise constriction and release, respectively, of an inferior vena caval occluder to vary Q. Surprisingly, after 10-15 min of hypoperfusion (Q decreased from 139 +/- 9 to 46 +/- 3 ml.min-1.kg-1), the pulmonary vascular pressure gradient (pulmonary arterial pressure-pulmonary capillary wedge pressure) was unchanged over a broad range of Q during reperfusion compared with base line when the ANS was intact. In contrast, pulmonary vasoconstriction was observed during reperfusion after combined sympathetic beta-adrenergic and cholinergic receptor block, after beta-block alone, but not after cholinergic block alone. The pulmonary vasoconstriction during reperfusion was entirely abolished by combined sympathetic alpha- and beta-block. Although sympathetic alpha-block alone caused pulmonary vasodilation compared with the intact, base-line P/Q relationship, no further vasodilation was observed during reperfusion. Thus the ANS actively regulates the pulmonary circulation during reperfusion in conscious dogs. With the ANS intact, sympathetic beta-adrenergic vasodilation offsets alpha-adrenergic vasoconstriction and prevents pulmonary vasoconstriction during reperfusion.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology*; D001784:Blood Gas Analysis; D004285:Dogs; D006439:Hemodynamics; D008297:Male; D010477:Perfusion; D011652:Pulmonary Circulation; D011669:Pulmonary Wedge Pressure; D011950:Receptors, Cholinergic / Q000378:metabolism; D014661:Vasoconstriction
D000319:Adrenergic beta-Antagonists; D011950:Receptors, Cholinergic