title: Phenylephrine-induced rhythmic activity in the rabbit ear artery.
abstract: Isolated rabbit ear arteries displayed rhythmic contractions when stimulated with alpha 1 agonist phenylephrine. These rhythmic responses were greatly attenuated by endothelium removal. However, contractions were sufficiently rhythmic in the arteries treated with NG-monomethyl-L-arginine, NG-nitro-L-arginine and indomethacin, synthetic inhibitors of endothelium-derived nitric oxide and prostanoids. Phenylephrine-induced rhythmic contractions were converted to tonic contractions by the blockade both of the voltage-dependent Ca2+ channel and the Ca(2+)-activated K+ channel by nifedipine and charybdotoxin, respectively. In contrast, glibenclamide, an ATP-sensitive K+ channel antagonist, did not alter the rhythmic contractions. These results suggest that endothelium may in part regulate the phenylephrine-induced rhythmic contractions in the rabbit ear artery, although endothelium-derived nitric oxide or prostanoids may not be involved in these responses. These endothelium-involved rhythmic responses may be attributed to the activation of the voltage-dependent Ca2+ channel and the Ca(2+)-activated K+ channel.
authors.affiliation: Development Laboratories Hirakata Center, Marion Merrell Dow, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Omote
authors.forename: H
authors.initials: H
authors.lastname: Mizusawa
mesh_terms: D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D018999:Charybdotoxin; D004431:Ear, External / Q000098:blood supply; D004730:Endothelium, Vascular / Q000502:physiology; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology; D019335:Nitroarginine; D010507:Periodicity; D010656:Phenylephrine / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D011448:Prostaglandin Antagonists; D011817:Rabbits; D012604:Scorpion Venoms / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology; D019323:omega-N-Methylarginine
chemical_list: D026902:Potassium Channel Blockers; D011448:Prostaglandin Antagonists; D012604:Scorpion Venoms; D018999:Charybdotoxin; D010656:Phenylephrine; D019335:Nitroarginine; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D009543:Nifedipine; D005905:Glyburide; D007213:Indomethacin