Alpha-adrenergic effects of dopamine and dobutamine on the coronary circulation.
After beta-adrenergic blockade, dopamine causes coronary vasoconstriction that is blocked by non-selective alpha-adrenergic antagonists. This study was carried out to determine the relative importance of alpha 1- and alpha 2-adrenoceptors in mediating coronary vasoconstriction in response to dopamine. Because dobutamine has been reported to cause alpha-adrenergic stimulation, the response to dobutamine was also examined. The circumflex coronary artery was cannulated and perfused at a constant blood flow rate in 14 dogs; coronary vasomotor responses were assessed from changes in perfusion pressure. Central effects were eliminated by vagotomy and stellate ganglionectomy; propranolol (1 mg/kg i.v.) was administered to block beta-adrenergic effects. The coronary responses to intracoronary bolus doses of dopamine and dobutamine were determined; the effects of selective alpha 1-blockade with prazosin (600 micrograms/kg i.v.) and selective alpha 2-blockade with idazoxan or rauwolscine (1-5 micrograms/kg per min intracoronary for 10 min) were examined. Dopamine produced dose-related coronary vasoconstriction; this response was not significantly altered by alpha 1-blockade with prazosin, but was abolished by the addition of alpha 2-adrenergic blockade with idazoxan or rauwolscine. Dobutamine did not produce coronary vasoconstriction at any dose tested. These data demonstrate that coronary vasoconstriction produced by dopamine is mediated through postjunctional alpha 2-adrenergic receptors.
Dai
X Z
XZ
Department of Internal Medicine, University of Minnesota Medical School, Minneapolis 55455.
Chen
D G
DG
Bache
R J
RJ
D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects*; D004146:Dioxanes / Q000494:pharmacology; D004280:Dobutamine / Q000494:pharmacology*; D004285:Dogs; D004298:Dopamine / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects; D019329:Idazoxan; D011433:Propranolol / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D004146:Dioxanes; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D004280:Dobutamine; D011433:Propranolol; D004298:Dopamine; D019329:Idazoxan