title: Local cerebral blood flow in the dog during intravenous infusion of dopamine.
abstract: Local cerebral blood flow was measured in anaesthetized beagle dogs by the hydrogen clearance method. Dopamine was administered as a continuous intravenous infusion of varying doses. The changes in local cerebral blood flow induced by dopamine were similar at the different locations; i.e., the caudate nucleus, thalamus, frontal and parietal cortex. Blood flow responded to dopamine in the following ways: low dose (less than 2 micrograms/kg/min): blood flow decreased or remained unchanged; moderate doses (2--6 micrograms/kg/min): blood flow increased at all electrodes; high doses (7--20 micrograms/kg/min): blood flow decreased once again. The decrease in blood flow could be inhibited by the alpha-adrenergic receptor antagonist phentolamine or by the serotonin receptor antagonist methysergide. This indicates that the constrictor effect of dopamine on cerebral blood vessels is mediated via alpha-adrenergic receptors as well as via serotonin receptors. The increase in cerebral flow could be inhibited by the dopamine receptor antagonist haloperidol, indicating vascular dopamine receptors in the brain with a dilating effect. When the vasoconstrictor activity of dopamine is blocked, the single response to a dopamine infusion is a blood flow increase. This might be beneficial in the clinical situation of symptomatic vasospasm.
mesh_terms: D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002536:Cerebral Arteries / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D004285:Dogs; D004298:Dopamine / Q000008:administration & dosage / Q000494:pharmacology*; D018492:Dopamine Antagonists; D006220:Haloperidol / Q000494:pharmacology; D000860:Hypoxia / Q000503:physiopathology; D007263:Infusions, Parenteral; D008784:Methysergide / Q000494:pharmacology; D011954:Receptors, Dopamine / Q000187:drug effects / Q000378:metabolism; D011985:Receptors, Serotonin / Q000187:drug effects; D012701:Serotonin; D012702:Serotonin Antagonists; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D018492:Dopamine Antagonists; D011954:Receptors, Dopamine; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D012701:Serotonin; D006220:Haloperidol; D000241:Adenosine; D001058:Apomorphine; D004298:Dopamine; D008784:Methysergide