title: Lidocaine impairs vasodilation mediated by adenosine triphosphate-sensitive K+ channels but not by inward rectifier K+ channels in rat cerebral microvessels.
abstract: Vasodilator effects of adenosine triphosphate (ATP)-sensitive, as well as inward rectifier, K+ channel openers have not been well demonstrated in cerebral microvessels. Although lidocaine impairs vasorelaxation via ATP-sensitive K+ channels in the rat aorta, the effects of this compound on K+ channels in the cerebral circulation have not been shown. We designed the present study to examine whether ATP-sensitive and inward rectifier K+ channels contribute to vasodilator responses in cerebral microvessels and whether the vasodilation mediated by these channels is inhibited by lidocaine. Rat brain slices were monitored using a computer-assisted videomicroscopy. Cerebral parenchymal arterioles (diameter, 5-10 microm) were contracted with prostaglandin F(2alpha), and thereafter potassium chloride (KCl), levcromakalim, or sodium nitroprusside was added to the perfusion chamber. Levcromakalim and KCl produced vasodilation of the cerebral parenchymal arterioles, which was abolished by an ATP-sensitive K+ channel antagonist, glibenclamide, or an inward rectifier K+ channel antagonist, barium chloride, respectively. Lidocaine (10(-5) to 3 x 10(-5) M) inhibited the dilation produced by levcromakalim but not by KCl or sodium nitroprusside. In parenchymal arterioles of the cerebral cortex, lidocaine seems to reduce vasodilation mediated by ATP-sensitive K+ channels but not by inward rectifier K+ channels.
authors.affiliation: *Department of Anesthesiology, Wakayama Medical University; and †Department of Anesthesia, Japanese Red Cross Society Wakayama Medical Center, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kinoshita
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Nakahata
authors.forename: Mayuko
authors.initials: M
authors.lastname: Dojo
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Kimoto
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hatano
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply*; D019806:Cromakalim / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008012:Lidocaine / Q000494:pharmacology*; D008297:Male; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000779:Anesthetics, Local; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D019806:Cromakalim; D000255:Adenosine Triphosphate; D008012:Lidocaine