title: Intestinal vascular responses to dopamine during fentanyl-nitrous oxide anaesthesia, supplemented with dixyrazin.
abstract: Intestinal haemodynamics in response to continuous i.v. administration of dopamine were investigated in cats anaesthetized with fentanyl-nitrous oxide either with or without supplement of dixyrazin. A dose-dependent vasodilatation was observed in the dopamine dose range 2.5-35 micrograms . kg-1 . min-1 and the subsequent maximal intestinal blood flow increase was 121%. No net intestinal vasoconstriction was evident even at the largest dopamine doses, although the vascular response reached a plateau at 17.5 micrograms . kg-1 . min-1. Control experiments during chloralose anaesthesia gave similar results. Changes in mean arterial pressure and heart rate were small. Renal blood flow was virtually unchanged at dopamine doses below 10 micrograms . kg-1 . min-1, while renal vasoconstriction was evident following dopamine doses above that level. The addition of i.v. dixyrazin (0.15-0.30 mg . kg-1) to the fentanyl-nitrous oxide anaesthesia substantially potentiated the intestinal vasodilator response to i.v. dopamine and the maximal blood flow increase was 183% at 10-15 micrograms . kg-1 . min-1. In vitro experiments using mesenteric resistance vessels from the rat demonstrated a dose-dependent relaxation to dopamine. At very large doses this response was counteracted, but not reversed into vasoconstriction by dopamine-induced alpha-adrenergic stimulation.
mesh_terms: D000818:Animals; D002415:Cats; D002698:Chloralose / Q000008:administration & dosage; D004298:Dopamine / Q000008:administration & dosage*; D004357:Drug Synergism; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage; D006439:Hemodynamics / Q000187:drug effects*; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000502:physiology*; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009609:Nitrous Oxide / Q000008:administration & dosage; D010640:Phenothiazines / Q000008:administration & dosage*; D051381:Rats; D012039:Regional Blood Flow / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
chemical_list: D010640:Phenothiazines; D002698:Chloralose; C012950:dixyrazine; D009609:Nitrous Oxide; D005283:Fentanyl; D004298:Dopamine