title: G protein-coupled endothelial receptor for atypical cannabinoid ligands modulates a Ca2+-dependent K+ current.
abstract: The cannabinoid analog "abnormal cannabidiol" (abn-cbd) causes endothelium-dependent vasodilation in rat isolated mesenteric arteries through a G protein-coupled receptor distinct from CB1 or CB2. We examined the actions of abn-cbd on the electrophysiology of human umbilical vein endothelial cells (HUVEC), using the whole cell version of the patch clamp technique. Voltage steps produced noninactivating outward currents, which were abolished by iberiotoxin or by chelation of intracellular calcium. The presence of a BKCa channel in HUVEC was documented by reverse transcriptase-PCR. Abn-cbd concentration dependently potentiated the outward current produced by a single voltage step. This potentiation was abolished by the cannabidiol analog O-1918 or by pertussis toxin but was unaffected by CB1 or CB2 antagonists. HU-210, a CB1/CB2 receptor agonist, had no effect on the outward current. Clamping [Ca2+]i did not prevent abn-cbd-induced increases in outward current. cGMP potentiated the outward current, and abn-cbd increased the cellular levels of cGMP. The increase in outward current produced by abn-cbd was blocked by KT-5823, an inhibitor of protein kinase G, or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), an inhibitor of soluble guanylate cyclase. We conclude that a Ca2+-activated K+ current in HUVEC is potentiated by activation of a Gi/Go-coupled receptor distinct from CB1 or CB2, which signals through cGMP and protein kinase G to increase channel availability or the sensitivity of the channel to voltage and/or Ca2+. Because iberiotoxin also inhibited abn-cbd-induced relaxation of intact, but not of endothelium-denuded, rat mesenteric artery segments, modulation of endothelial BKCa channels may underlie the mesenteric vasodilator action of abn-cbd.
authors.affiliation: Laboratories of Physiologic Studies and of Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892, USA.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Begg
authors.forename: Fong-Ming
authors.initials: FM
authors.lastname: Mo
authors.forename: László
authors.initials: L
authors.lastname: Offertaler
authors.forename: Sándor
authors.initials: S
authors.lastname: Bátkai
authors.forename: Pál
authors.initials: P
authors.lastname: Pacher
authors.forename: Raj K
authors.initials: RK
authors.lastname: Razdan
authors.forename: David M
authors.initials: DM
authors.lastname: Lovinger
authors.forename: George
authors.initials: G
authors.lastname: Kunos
mesh_terms: D000818:Animals; D001158:Arteries / Q000166:cytology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002186:Cannabinoids / Q000737:chemistry*; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004594:Electrophysiology; D004727:Endothelium / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006162:Guanylate Cyclase / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D008024:Ligands; D008297:Male; D008564:Membrane Potentials; D010069:Oxadiazoles / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012118:Resorcinols / Q000737:chemistry* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014471:Umbilical Veins / Q000166:cytology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; C479832:4-(3-3,4-p-menthadien-(1,8)-yl)olivetol; D002186:Cannabinoids; D002227:Carbazoles; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D007211:Indoles; D008024:Ligands; D010069:Oxadiazoles; D010455:Peptides; D015221:Potassium Channels; D011810:Quinoxalines; D012118:Resorcinols; D014665:Vasodilator Agents; C073601:KT 5823; C064719:iberiotoxin; D013759:Dronabinol; D037342:Pertussis Toxin; D006162:Guanylate Cyclase; D006152:Cyclic GMP; C062018:HU 211; D011188:Potassium; D002118:Calcium