ATP-sensitive K+ channels mediate dilatation of cerebral arterioles during hypoxia.
We tested the hypothesis that dilatation of cerebral arterioles during hypoxia is mediated by activation of ATP-sensitive K+ channels. The diameter of pial arterioles was measured through a closed cranial window in anesthetized rabbits. Topical application of aprikalim (10(-6) mol/L), a direct activator of ATP-sensitive K+ channels, dilated pial arterioles by 18 +/- 3% (mean +/- SEM). Glibenclamide (10(-6) mol/L), an inhibitor of ATP-sensitive K+ channels, virtually abolished aprikalim-induced vasodilatation. When arterial PO2 was reduced from 129 +/- 3 to 25 +/- 1 mm Hg, the diameter of cerebral arterioles increased by 66 +/- 9% (P < .05). Glibenclamide inhibited dilatation of pial arterioles during hypoxia by 46 +/- 5% (P < .05). In contrast, vasodilatation in response to sodium nitroprusside was not altered by glibenclamide. Topical application of adenosine (10(-4) mol/L) increased arteriolar diameter by 21 +/- 4%. Glibenclamide did not affect adenosine-induced vasodilatation. These findings suggest that dilatation of cerebral arterioles in response to hypoxia is mediated, in part, by activation of ATP-sensitive K+ channels.
Taguchi
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Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
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Kitazono
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D000241:Adenosine / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000503:physiopathology; D001921:Brain / Q000098:blood supply*; D005905:Glyburide / Q000494:pharmacology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D010847:Picolines / Q000494:pharmacology*; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D011714:Pyrans / Q000494:pharmacology*; D011817:Rabbits; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D010847:Picolines; D015221:Potassium Channels; D011714:Pyrans; C061043:aprikalim; D000255:Adenosine Triphosphate; D000241:Adenosine; D005905:Glyburide